Oddbean new post about login | logout Clients like forums can put a comment 'this reply was made before the original post was edited' so not really an issue.
Which Nostr clients do that, again? Its not really an issue once they all do
None as far as I know. But I see no reason this couldn't be implemented once we have edit/deletes using timestamps.
The delete removes things from relays, so while clients need to trigger the delete request, it’s the relay that honors it. You can use nos.social to delete content, but you can also just use this web app: https://nostr-delete.vercel.app/