And the 3 most popular relay implementations all support NIP-09 (event deletion). Not really sure why we keep repeating that posts can’t be deleted.

There is truth of course to the idea that you don’t know if a relay is truly deleting the event from disk even if they tell you they are. You also don’t know what other relays have stored that event and there could be many that you don’t even know about syncing from other relays.