Amethyst can request relays to delete notes.
Discussion
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.
Wondering about our European friends. Would think that relay operators in the EU would be bound by the GDPR laws. Meaning a node operator in the EU, would need to remove a user's data on request. I'm not an expert on this topic though.