diff --git a/bbs/menu.c b/bbs/menu.c
index 7165eb24..20b5d210 100644
--- a/bbs/menu.c
+++ b/bbs/menu.c
@@ -470,6 +470,8 @@ static int menu_set_title(struct bbs_node *node, const char *name)
 	return bbs_node_set_term_title(node, stripped);
 }
 
+#define SCRATCH_BUF_SIZE 256
+
 /*!
  * \brief Run the BBS on a node
  * \param node node
@@ -477,7 +479,7 @@ static int menu_set_title(struct bbs_node *node, const char *name)
  * \param stack Current stack count
  * \param optreq Option request string
  */
-static int bbs_menu_run(struct bbs_node *node, const char *menuname, const char *menuitemname, int stack, const char *optreq)
+static int bbs_menu_run(struct bbs_node *node, const char *menuname, const char *menuitemname, int stack, const char *optreq, char *restrict scratchbuf)
 {
 	int res;
 	char opt = 0;
@@ -653,13 +655,15 @@ static int bbs_menu_run(struct bbs_node *node, const char *menuname, const char
 		 * we need to be able to recurse efficiently with arguments that other handlers don't (and shouldn't) get. */
 		if (STARTS_WITH(menuitem->action, "menu:")) {
 			/* Execute another menu, recursively */
-			res = bbs_menu_run(node, menuitem->action + 5, menuitem->name, stack, optreq ? optreq + 1 : NULL);
+			res = bbs_menu_run(node, menuitem->action + 5, menuitem->name, stack, optreq ? optreq + 1 : NULL, scratchbuf);
 		} else {
 			char *handler, *args;
-			/* At this point in the function, we're done with the options buffer, and if we need it again, we'll fill it again.
-			 * So, reuse that buffer since we're in a recursive function, and we really want to avoid stack allocations if possible. */
-			safe_strncpy(options, menuitem->action, sizeof(options));
-			handler = options;
+			/* We need a buffer that is sufficiently long enough to avoid truncation, so use the scratch buffer. */
+			safe_strncpy(scratchbuf, menuitem->action, SCRATCH_BUF_SIZE);
+			if (strlen(scratchbuf) >= SCRATCH_BUF_SIZE - 1) {
+				bbs_warning("Truncation occurred copying menu item arguments into buffer of size %d\n", SCRATCH_BUF_SIZE);
+			}
+			handler = scratchbuf;
 			args = strchr(handler, ':');
 			if (args) {
 				*args++ = '\0'; /* We just want the name of the menu handler to use. */
@@ -723,7 +727,10 @@ static int bbs_menu_run(struct bbs_node *node, const char *menuname, const char
 
 int bbs_node_menuexec(struct bbs_node *node)
 {
-	return bbs_menu_run(node, DEFAULT_MENU, NULL, 0, NULL);
+	/* Declare just once rather than on each stack frame, since bbs_menu_run recurses a lot.
+	 * This allows us to save (BBS_MAX_MENUSTACK - 1) * SCRATCH_BUF_SIZE bytes of stack space. */
+	char scratchbuf[SCRATCH_BUF_SIZE];
+	return bbs_menu_run(node, DEFAULT_MENU, NULL, 0, NULL, scratchbuf);
 }
 
 static int load_config(int reload)
diff --git a/bbs/variables.c b/bbs/variables.c
index de98d290..c250e47c 100644
--- a/bbs/variables.c
+++ b/bbs/variables.c
@@ -433,7 +433,7 @@ const char *bbs_node_var_get(struct bbs_node *node, const char *key)
 	return value;
 }
 
-int bbs_node_var_get_buf(struct bbs_node *node, const char *key, char *buf, size_t len)
+int bbs_node_var_get_buf(struct bbs_node *node, const char *key, char *restrict buf, size_t len)
 {
 	const char *s;
 
@@ -459,7 +459,7 @@ int bbs_node_var_get_buf(struct bbs_node *node, const char *key, char *buf, size
 	return s ? 0 : -1;
 }
 
-int bbs_node_substitute_vars(struct bbs_node *node, const char *sub, char *buf, size_t len)
+int bbs_node_substitute_vars(struct bbs_node *node, const char *sub, char *restrict buf, size_t len)
 {
 	char varname[64];
 	char *bufstart = buf;
diff --git a/doors/door_irc.c b/doors/door_irc.c
index f5dcce8e..1a1cab2c 100644
--- a/doors/door_irc.c
+++ b/doors/door_irc.c
@@ -159,15 +159,19 @@ static int __chat_send(struct client_relay *client, struct participant *sender,
 
 	/* If sender is set, it's safe to use even with no locks, because the sender is a calling function of this one */
 	if (sender) {
-		bbs_debug(7, "Broadcasting %s to %s,%s (except node %d): %s%.*s\n", dorelay ? "to IRC" : "from IRC", client->name, channel, sender->node->id, datestr, len, msg);
+		bbs_debug(7, "Broadcasting %s -> %s,%s (except node %d): %s%.*s\n", dorelay ? "to IRC" : "from IRC", client->name, channel, sender->node->id, datestr, len, msg);
 	} else {
-		bbs_debug(7, "Broadcasting %s to %s,%s: %s%.*s\n", dorelay ? "to IRC" : "from IRC", client->name, channel, datestr, len, msg);
+		bbs_debug(7, "Broadcasting %s -> %s,%s: %s%.*s\n", dorelay ? "to IRC" : "from IRC", client->name, channel, datestr, len, msg);
 	}
 
 	/* Relay the message to everyone */
 	RWLIST_RDLOCK(&client->participants);
 	if (dorelay) {
-		bbs_irc_client_send(client->name, channel, msg); /* Actually send to IRC */
+		char prefix[32] = "";
+		if (sender) { /* XXX Can this ever be NULL here? */
+			snprintf(prefix, sizeof(prefix), "%s@%u", bbs_username(sender->node->user), sender->node->id);
+		}
+		bbs_irc_client_msg(client->name, channel, prefix, "%s", msg); /* Actually send to IRC */
 	}
 	RWLIST_TRAVERSE(&client->participants, p, entry) {
 		ssize_t res;
@@ -415,6 +419,7 @@ static int irc_single_client(struct bbs_node *node, char *constring, const char
 	char usernamebuf[24];
 	char passwordbuf[64];
 	char buf[2048];
+	int underscores = 0;
 	char *username, *password, *hostname, *portstr;
 
 	/* Parse the arguments.
@@ -584,11 +589,14 @@ static int irc_single_client(struct bbs_node *node, char *constring, const char
 			 * so just pass 0 as poll should always return > 0 anyways, immediately,
 			 * since we haven't read any data yet to quell the poll. */
 
-			/* Another clunky thing. Need to get data using irc_read, but we want to buffer it using a bbs_node_readline struct.
+			/* Another clunky thing. Need to get data using irc_read, but we want to buffer it using a readline_data struct.
 			 * So use bbs_readline_append.
 			 */
 			bres = irc_read(ircl, tmpbuf, sizeof(tmpbuf));
-			res = bbs_readline_append(&rldata, "\r\n", tmpbuf, (size_t) res, &ready);
+			if (bres <= 0) {
+				break;
+			}
+			res = bbs_readline_append(&rldata, "\r\n", tmpbuf, (size_t) bres, &ready);
 			if (!ready) {
 				continue;
 			}
@@ -609,6 +617,22 @@ static int irc_single_client(struct bbs_node *node, char *constring, const char
 					switch (irc_msg_type(msg)) {
 						case IRC_NUMERIC:
 							bbs_node_writef(node, "%s %d %s\n", NODE_IS_TDD(node) ? "" : S_IF(irc_msg_prefix(msg)), irc_msg_numeric(msg), irc_msg_body(msg));
+							switch (irc_msg_numeric(msg)) {
+								case 433: /* Nickname in use - very likely to happen if already logged in using a regular IRC client */
+									if (underscores++ < 5) {
+										char newnick[32];
+#define UNDERSCORES "_____"
+										snprintf(newnick, sizeof(newnick), "%s%.*s", irc_client_username(ircl), underscores, UNDERSCORES);
+										bbs_debug(1, "Auto-changing nickname to '%s' to avoid conflict\n", newnick);
+										irc_client_change_nick(ircl, newnick);
+										/* Assuming this succeeds, try joining the channel we intended to,
+										 * since that would have failed. */
+										irc_client_channel_join(ircl, channel);
+									}
+									break;
+								default:
+									break;
+							}
 							break;
 						case IRC_CMD_PRIVMSG:
 						case IRC_CMD_NOTICE:
diff --git a/include/variables.h b/include/variables.h
index 7e7b5abc..4e9eb877 100644
--- a/include/variables.h
+++ b/include/variables.h
@@ -137,7 +137,7 @@ const char *bbs_node_var_get(struct bbs_node *node, const char *key);
  * \param len Size of buf.
  * \retval 0 if found, -1 if not found
  */
-int bbs_node_var_get_buf(struct bbs_node *node, const char *key, char *buf, size_t len);
+int bbs_node_var_get_buf(struct bbs_node *node, const char *key, char *restrict buf, size_t len);
 
 /*!
  * \brief Substitute variables in a string
@@ -147,4 +147,4 @@ int bbs_node_var_get_buf(struct bbs_node *node, const char *key, char *buf, size
  * \param len Size of buf.
  * \retval 0 if found, -1 if not found
  */
-int bbs_node_substitute_vars(struct bbs_node *node, const char *sub, char *buf, size_t len);
+int bbs_node_substitute_vars(struct bbs_node *node, const char *sub, char *restrict buf, size_t len);
diff --git a/nets/net_irc.c b/nets/net_irc.c
index c5bc97e1..c0b47957 100644
--- a/nets/net_irc.c
+++ b/nets/net_irc.c
@@ -2282,12 +2282,38 @@ static void broadcast_nick_change(struct irc_user *user, const char *oldnick)
 	RWLIST_UNLOCK(&channels);
 }
 
+static void do_identity_update(struct irc_user *user)
+{
+	if (!user->registered) {
+		add_user(user);
+	} else {
+		hostmask(user);
+	}
+}
+
 static void handle_nick(struct irc_user *user, char *s)
 {
 	if (user->node->user && strcasecmp(s, bbs_username(user->node->user))) {
-		/* Don't allow changing nick if already logged in, unless it's to our actual username. */
-		send_numeric(user, 902, "You must use a nick assigned to you\r\n");
-	} else if (bbs_user_exists(s)) {
+		const char *suffix;
+		size_t usernamelen = strlen(bbs_username(user->node->user));
+		/* Don't allow changing nick if already logged in, unless it's to our actual username,
+		 * or something that starts with it, followed by an underscore. */
+		if (strncasecmp(s, bbs_username(user->node->user), usernamelen)) {
+			send_numeric(user, 902, "You must use a nick assigned to you\r\n");
+			return;
+		}
+		/* If username is jsmith, allow jsmith_, jsmith__, jsmith_m, etc.
+		 * But it has to be jsmith or start with jsmith_ */
+		suffix = s + usernamelen;
+		/* If the first n characters match but not the whole string the suffix must be non-empty */
+		bbs_assert(!strlen_zero(suffix));
+		if (*suffix != '_') {
+			send_numeric(user, 902, "You must use a nick assigned to you\r\n");
+			return;
+		}
+	}
+
+	if (bbs_user_exists(s)) {
 		send_numeric(user, 433, "%s :Nickname is already in use.\r\n", s);
 		send_reply(user, "NOTICE AUTH :*** This nickname is registered. Please choose a different nickname, or identify using NickServ\r\n");
 		/* Client will need to send NS IDENTIFY <password> or PRIVMSG NickServ :IDENTIFY <password> */
@@ -2307,9 +2333,10 @@ static void handle_nick(struct irc_user *user, char *s)
 		}
 		user->nickname = newnick;
 		RWLIST_UNLOCK(&users);
+		do_identity_update(user);
 		if (!s_strlen_zero(oldnick)) {
 			send_reply(user, ":%s NICK %s\r\n", oldnick, user->nickname);
-			broadcast_nick_change(user, oldnick); /* XXX Won't actually traverse, if registered users aren't allowed to change nicks? */
+			broadcast_nick_change(user, oldnick);
 		}
 	}
 }
@@ -2341,11 +2368,7 @@ static void handle_identify(struct irc_user *user, char *s)
 		if (strlen_zero(user->nickname) || strcasecmp(username, user->nickname)) {
 			REPLACE(user->nickname, username);
 		}
-		if (!user->registered) {
-			add_user(user);
-		} else {
-			hostmask(user);
-		}
+		do_identity_update(user);
 		send_numeric(user, 900, IDENT_PREFIX_FMT " %s You are now logged in as %s\r\n", IDENT_PREFIX_ARGS(user), user->username, user->username);
 	}
 }
@@ -2945,9 +2968,9 @@ static int do_sasl_auth(struct irc_user *user, char *s)
 		send_numeric(user, 904, "SASL authentication failed\r\n");
 		return -1;
 	}
-	send_numeric(user, 903, "SASL authentication successful\r\n");
 	/* The prefix is nick!ident@host */
 	send_numeric(user, 900, IDENT_PREFIX_FMT " %s You are now logged in as %s\r\n", IDENT_PREFIX_ARGS(user), user->username, user->username);
+	send_numeric(user, 903, "SASL authentication successful\r\n");
 	return 0;
 }
 
@@ -3028,15 +3051,14 @@ static void handle_client(struct irc_user *user)
 					if (!started) {
 						/* Users that aren't started, and more importantly, in the user list, (!started, !user->registered)
 						 * can change their nickname arbitrarily, but can't use it without identifying. */
-						user->nickname = strdup(s);
+						REPLACE(user->nickname, s);
 						bbs_debug(5, "Nickname is %s\n", user->nickname);
 					}
 				} else if (!strcasecmp(command, "USER")) { /* Whole message is something like 'ambassador * * :New Now Know How' */
 					char *realname;
 					bbs_debug(5, "Username data is %s\n", s);
 					realname = strsep(&s, " ");
-					free_if(user->realname);
-					user->realname = strdup(realname);
+					REPLACE(user->realname, realname);
 					if (handle_user(user)) {
 						break;
 					}
@@ -3098,7 +3120,10 @@ static void handle_client(struct irc_user *user)
 						bbs_error("Client %p already started?\n", user);
 					}
 				} else {
+					char *command;
 					bbs_warning("Unhandled message: %s\n", s);
+					command = strsep(&s, " ");
+					send_numeric2(user, 421, "%s :Unknown command or invalid in current state\r\n", command);
 				}
 			} else {
 				bbs_warning("Unhandled message: %s\n", s);
@@ -3166,7 +3191,7 @@ static void handle_client(struct irc_user *user)
 				send_reply(user, "NOTICE AUTH :*** This server requires SASL for authentication. Please reconnect with SASL enabled.\r\n");
 				goto quit; /* Disconnect at this point, there's no point in lingering around further. */
 			/* We can't necessarily use %s (user->username) instead of %p (user), since if require_sasl == false, we might not have a username still. */
-			} else if (!user->node->user) {
+			} else if (!user->node->user || !user->registered) {
 				char *target;
 				/* Okay to message NickServ without being registered, but nobody else. */
 				/* Can be NS IDENTIFY <password> or a regular PRIVMSG */
@@ -3186,7 +3211,13 @@ static void handle_client(struct irc_user *user)
 						continue;
 					}
 				}
-				send_numeric(user, 451, "You have not registered\r\n");
+				if (!user->node->user) {
+					send_numeric(user, 451, "You have not registered\r\n");
+				} else {
+					send_numeric(user, 433, "Nickname is already in use\r\n");
+				}
+			} else if (!user->registered) {
+				send_numeric(user, 433, "Nickname is already in use\r\n");
 			} else if (!strcasecmp(command, "NS")) { /* NickServ alias */
 				nickserv(user, s);
 			} else if (!strcasecmp(command, "CS")) { /* ChanServ alias (much like NS ~ NickServ) */
@@ -3376,7 +3407,7 @@ static void handle_client(struct irc_user *user)
 			/* Ignore SQUIT for now, since this is a single-server network */
 			} else {
 				send_numeric2(user, 421, "%s :Unknown command\r\n", command);
-				bbs_warning("%p: Unhandled message: %s %s\n", user, command, s);
+				bbs_warning("%p: Unhandled message: %s %s\n", user, command, S_IF(s));
 			}
 		}
 	}