I have been having this exact same issue across multiple websites recently, most of the time it's monospace fonts that have the issue - Github is a nightmare. It only started after I upgraded to Fedora 42.

Haven't got to the bottom of it yet. I set Victor Mono as my Monospace font in Chrome and that has fixed it for things like the HN comment box, for instance, but Github and such still all look weird.

I've can't remember ever seeing this particular glitch before in my 20+ year Linux usage history. Very weird.