Every time I scroll down a page, after a little while (5-20sec) it scrolls itself up, usually to the top comment but sometimes (I think based on how far down I am) just further up. I don't usually pull out 'literally unusable', but here we are. No problems on lemmy.ml (not logged in). Firefox with normal privacy add-ons on Fedora 38. Have I got something set to evil? Wasn't happening a week or so ago.
Yeah the auto updating content that is jerking the page around is really a horrendous user experience and I am sure lots of people thinking about giving the site a try is seeing it and noping out immediately.
I think they've fixed that in v18. Lemmy.world doesn't plan to update until v18.1 gets released, due to an unrelated regression (no captcha on sign up page).
But plenty of other instances have updated. If you create an account on lemmy.ml or lemmy.ca, you'll have a much better experience.
Not sure if it is browser specific. I am using Firefox. I would guess that it is a feature from when the site was much less active but now that there are things being added much more often it just makes the site very hard to use.