i think there are a couple of things but i'd have to think about it. a big one that was recently implemented across many servers was editing. when you edit a post, others can see that it was edited and you can check the edit history if you want. also, if you repost something and it gets edited, you get a notification about it, so you can check if you still approve of what you reposted. but you can't withdraw anything on Nostr. you can't undo a like or a repost.