might be able to whip something up with tampermonkey - inject a link into every post that toggles "height: 200px; overflow: hidden" on the corresponding toplevel_item div, but that's an evening's work because i am too unfamiliar with the environment and would have to figure out where to put everything, how to select and so on :(

the problem is that friendica is extremely idiosyncratic about the amount of replies to a post it displays, and it can end up making it a chore to scroll through the feed. so, ideally, the script would remember which posts were collapsed, and that definitely doesn't sound like something i'd be able to whip up in an evening

looks like ublock origin may be the currently easiest solution. using the element picker, i can isolate the comments on a specific post and filter them out - then, if i want to see them again, i can turn off cosmetic filtering for the page temporarily.