To prevent the relay from knowing who is sending messages to whom, there is NIP-17. And there is NIP-104.
https://github.com/nostr-protocol/nips/blob/2169fab971591d0b4a450ef08aeb6301c5d2a0da/104.md

It confuses me that in your client, the relay sees participants in communication.

Don't think that I'm against paid messages, I realized that they are needed.