How? I don't see a delete button anywhere.

Who is the operator of your DM inbox relays? Gotta ask them. They can delete your messages.

Yes, manually finding out who the operator is and asking every single one to delete unwanted messages is truly a production ready chat experience.

I keep saying... You either control your relays or you don't own shit on nostr.

Ill pair the critisism with a proposal. It needs a NIP or something that does two things. First it tells the clients receiving the nip that anything prior should be treated as deleted. Second, it should tell the compatible relays the messages no longer have to be stored. That way if someone sends some unsolicited stuff or simply a conversation I am not interested in I can actually get rid of it properly and declutter. Right now on Matrix I can simply leave the room, the DM experience is great there. Nostr is an incomplete and incompatible mess on this front. It needs fixing, not workarounds.