i think a button like this wld be useful for threads or long pages where you quickly want to jump to the latest post and itd also be generally useful if you just wanna quickly jump to the top of the page as well
I still think this could be a good feature. Not all physical keyboards have Home and End keys, and mobile devices typically can't take advantage of browser key bindings.
STARLONG: well botb isn't exactly the most mobile friendly website to begin with so i'd say that a well-executed swipe will get you to the bottom/top of most threads in about a second or two
to be fair i did forget that the home/end key sorta does this already, maybe such a thing can be implemented with a tamper monkey or grease monkey script as well, i'll look into it at some point if it doesnt get implemented