Questions about Vietnamese diacritics

[LuoZijun]

I made an HTML page that renders Vietnamese accented letters, which should make it easier to see which characters are not well supported.

HTML Page: https://gist.github.com/LuoZijun/2e3cf3786ef93e576b1d2d855f1546ca

The following two pictures are the rendering results , Noto Sans Mono looks is good (the first picture).

[frankrolf]

Thank you again for this exhaustive explanation. Just to be clear – the pre-composed Vietnamese letters will not be changed. The statement “glyph looks weird” is subjective – and when you have a look on https://vietnamesetypography.com, you will see many designs following the same principle.
Pre-composed glyphs for Vietnamese with stacked accents are responsible for the tallest glyphs, and any change to make them taller will require setting larger vertical metrics – I would like to avoid that.

What potentially could change is a modification of the OT features, to result in vertical stacking when combining marks are used (rather than using the pre-composed code point). However, this depends on technical feasibility.

[frankrolf]

It might well be that I am misunderstanding something. Some specific questions:

• What is the reason for marking all “hook” characters? Perhaps it’s the missing vertical extender (question-mark like)? This is a deliberate design decision, an attempt at making the shape clear while being vertically compact.
• Why are all I-variants in Source Code Pro marked? The horizontal serif? This serif is essential for filling space (the wide gap created by I is problematic in word context). This solution can be found in most monospaced fonts.
• Presumably, the circumflexacute/circumflexgrave glyphs are marked because they are not stacking vertically. To that (from https://vietnamesetypography.com/design-challenges/):

The position of the diacritical marks can vary. As illustrated here, accents can be placed on the right side of a circumflex, on either side (usually an acute on the right and a grave on the left), or on the top. Accents on the right are ideal for consistency and the natural flow of text. Accents on either side are more distinguishable, but might slow down the process of saccades. Accents on the top are more balanced, but might affect the leading. For the ease and comfort of reading, accents (including a hook above) positioned consistently on the right are recommended, but type designers should choose the positions that best fit their design.