Another suggestion of mine would be to merge all reposts of a given event together and put it on top, ranked on most unread repostings, with the score decreasing as you scroll trough more and more recent posts. (When clicking at the ranked message on the top, you should be able to scroll that (aka the latest repost) into view, and after that only the original post will be shown.)

If there is something that is annoying, its those cluttering reposts. Now, we (client and relay) could effectively use them as a rating signal.)