routeEdge sometimes cuts corners or doubles back

[timothypratley]

routeEges usually succeeds in building a sensible edge line, but here is an example where it gets a little confused:

In the above example, a small wriggle gets introduced.

I suspect that the visibility graph is allowing links that cut through the bottom left corner of nodes.
I only ever see these effects overlapping the bottom left corner. Below is an example where you can see the same effect without a wriggle, it simply passes through the bottom left corner instead of routing down and around it:

Please let me know if there is a good method to help diagnose this further.