Yes, very annoying. Sometimes I cannot force it to stay long enough to read the posts, it just insists on jumping to the bottom of the page. Firefox.
I dislike Chrome so do not use it.
And for me. It makes it impossible to read some threads. I'm not sure exactly when it happens - it's not just scrolling with the mouse for me, cursor keys too. I thought it might be the feedback anoyance causing it but I'm not sure. I use Firefox but if a thread looks interesting enough and I can't read it I'll open it in MS Edge which doesn't seem to have the same issue.
Yes, very annoying. On Windows, the problem can be mitigated to some extent by pushing the title bar to the top of the screen (thus forcing the window height to expand to height of screen). Though this doesn't work all the time. I think the issue is caused by by the web page refreshing something at the top of the page which when scrolled off screen causes the jumping.
Note, holding the elevator when reading works too, but it is impossible to do this while replying.
Interesting - I have LOTS of issues with this forum, but random scrolling isn't among them. I use Edge. But, yes, pages with elements not fully loaded when you start reading can cause the page to jump around. I see this a lot on sites with ads (even with an ad blocker). It makes me wonder if there's some delay-loaded element at work here. Perusing uBlock Origin's log, I see there is content from AddThis that is blocked - that often adds a little widget for sharing a post/page with social media. That is a likely culprit.
I do not use an add blocker and I give the thread up to 10 minutes to make sure it is fully loaded but it still jumps to the bottom, but sometimes if it has a new reply it works normal again.
Got the problem today. It doesn't seems to depend of the window's height. I found that it seems to be related to a feature trying to display the whole footer of the page (company information, site map ...) when the page is scrolled down to a certain value.