I was wondering if there is any existing discussion of how to do private DMs. Seems to me like it should be possible, perhaps even relatively straightforward. Just send a DM that says "DM me at ", and then the receiver can accept that offer with their own new random npub. The relays will only see that there was one DM from A to B, and after that they will only see communication between two anonymous npubs (but no way to associate back to A and B).

The new npubs could of course be derived in some reasonable way to get them back later. Clients would need to support separate signing keys for DMs.

Haven't seen anything about this though, so I'm just spitballing.