Okay so now that Cohost has a lot more folks posting on it regularly, I have some thoughts about ways in which the UX could be a lot better.
The big thing that I have trouble with is it being a scrolling-based timeline but which doesn't have infinite scroll. The problem with the infinite scroll is less the "infinite" part but more the "scroll" part, but the "infinite" part is a partial fix to some of the more egregious problems of the "scroll" part. It's really difficult to actually stay caught up on things when you have a couple of screenfuls of things and then you have to click a button to continue, and it's especially hard to tell what you're not caught up on when you have to remember what you've seen. Reposts make it even more difficult because you're never sure if the thing you see at the bottom of the page is the last time you saw it, or if it's a new repost since the last time you saw it.
So what I'd really much rather see UX-wise is an "inbox" view, where new-to-you items show up in an inbox, and duplicate reposts of it get collapsed down into a single post, and reposts-with-additions get shown as, like, a thread or something. Think how email threads work, pretty much. Things you've already seen but which have gotten new comments could get a secondary indicator about that.