Simple improvement to DM privacy: send someone a new private key, which both of you can use to send encrypted "DMs to self".
At least message counts and timestamps will be hidden, and the fact that the other participant replied to your DM request.
Discussion
Cool 🤙 everyone is like “mad guy talking to himself “ lol 😂
You also get plausible deniability that "it was the other guy who sent that message" 😄
Really like the idea though I tried it over Instagram with my girlfriend in past😂
I guess another solution is to calculate a shared secret between your public keys, and tag messages with its hash instead of the recipient's pubkey.
Then nobody knows who you're talking to, but you need to subscribe to lots of tags that might never message you. And the relay still knows who subscribe to the same tags.
If this is automated, the new private key can be ECDH derived so it's always the same and independent of which one of you started the chat