"Please don't complain about website formatting, back-button breakage, and similar annoyances. They're too common to be interesting. Exception: when the author is present. Then friendly feedback might be helpful."
I don't mean to pick on you personally—the problem is more that these things tend to get upvoted to the top of the thread, where they choke out on-topic conversation. This happens because the annoyances are real, not because they're unreal. At the same time this comes up so often that we have to try to avoid the repetition.
In this particular case, the way the site semi-periodically twitches is kind of interesting itself. Way more than the common annoyances that you rightly chastise people for complaining about.
1. There are no apparent ads on the site. There are three things uBlock origin blocks, but they don't seem to be things doing anything visible (I'd guess trackers).
Usually it is sites infested with ads and a ton of trackers where you encounter visual glitches this jarring.
2. The interval between glitches varies, and sometimes it is a double glitch instead of a single glitch.
3. If I open the site in both Firefox and Chrome, their glitches are in sync. Same if I open it in more than one Firefox or Chrome window.
This suggests whatever it is doing is based on clock time, not on time since page load which is what I would have expected.
I agree in general. In this particular case, though, it was jarring. Having the screen jump every few seconds without the user interacting at all is a bit extreme.
https://news.ycombinator.com/newsguidelines.html
I don't mean to pick on you personally—the problem is more that these things tend to get upvoted to the top of the thread, where they choke out on-topic conversation. This happens because the annoyances are real, not because they're unreal. At the same time this comes up so often that we have to try to avoid the repetition.