Newer versions of browsers tend to re-adjust the scroll position to account for that.
However, based on chat in IRC, it appears mobius's issue actually is related to that he uses the "display newest posts at the top" option. Since this option is very rarely used (I believe), I can see why even in SMF itself, let alone a mod or my own changes (if the latter are relevant - now that I think about it, didn't I make a minor change to how it worked at some point?), might have missed a problem that occurs only with such an option. I will look into it later tonight.
I can confirm that I myself don't have this issue with either newest Firefox under Windows 10, newest Chromium under Ubuntu / LXDE, or newest Firefox Mobile under Android 4.4. However, I don't use the reverse order setting.