When you open a topic, the currently selected post fades in a certain color. Here on meta for dark theme, it’s a blue color, fading to the normal black. Recently this started getting jittery towards the end of the transition, instead of transitioning smoothly. I first noticed this on community.wanikani.com’s dark theme, but it’s happening here on meta as well. I’ve seen this using both Chrome and Edge across two different computers. Another Discourse site I use, which I’m fairly certain is quite a bit behind latest, does not exhibit this problem. If there’s a way for me to check the version of that site from the browser console (and if that information would be useful) let me know and I’ll add that information here.
See the video below for a demonstration.