> Moreover, delete both for me and for my contact. Is that too much to ask? Keybase chat allows you to delete messages on both yours and the recipient's side after a set time limit.

If this feature made it to any open-source or public protocols, it'd be pretty much impossible to guarantee that your message is actually deleted on the recipient's side. Someone could always make a 3rd party client that ignores the request. Or a user could just take a screenshot/etc.

I didn't see you mention it, so I'd recommend looking at Matrix / Element. It's decentralized in the way that e-mail is decentralized. It's federated and allows e2e.

https://matrix.org/

https://element.io/