[toast0]

I think this comment gets at the root of the issue. This is syntax highlighting, but it's done by the font rendering engine and it has no context.

Syntax highlighting without context is not really a good experience. The highlighter needs to know what language you're using, and a pretty good idea of how to parse it.

And the comment on ligatures below points out, this is actually true of ligatures for human languages as well, but I doubt the font engines are properly tuned for that either. I'd make an exception for the 'obvious' ligatures like gg gy etc where the descenders were overlapping without a ligature. That shouldn't be an issue in a monospaced context though.