Let me maybe give another explanation of how i came to this issue.
In extremely long posts i can press j to scroll (instead of mouse) because of Smooth J/K navigation when using keyboard. <- But that feature is half broken for me since i only read about 3/4 of the screen bejore pressing j, so that makes me lose some text (the 1/4 at the bottom of the screen has 2, 3 rows hidden).
Secondly, it really doesn’t work properly when i use 175% zoom on my 12 inch 2 in 1 laptop, especially if i pinch-to-zoom (note that i’m using chrome here. firefox’s touch implementation is unusable).
My third pet-peve is that when i am almost at the bottom of the post (the part with like, reply, etc buttons), j jumps too soon to the next post (eg, i would like it to show me the bottom of the post just under half of the screen, so i can see clearly that the post is finished).
Because of all these, whenever i have a long post, i still use my mouse/touchpad instead of pressing j to read. After than, i keep on using my touchpad for a little while until i remember than pressing j is easier.
Problem is that if i dont specifically click the current post onscreen, the first time i press j everything is broken as i see some post i have already read previously.
Basically you may say i have 2 different problems: the first one is with smooth navigation which jumps too soon to the next “portion” (be it of the post, or next post) and the second is that current post selection is not in sync with the address bar.