Thanks! NIP-42 sounds interesting. Could bring in new use-cases like paid groups
Yes, nostream support pubkey whitelist to make it semi private https://github.com/Cameri/nostream (anyone can read, only whitelisted member can write)
Furthermore, with NIP-42 can make relay more private (read and write only for whitelisted)
Discussion
Agree, lets say we have family group relay, company group relay, etc. Just need to wait all relay and client implement this NIP.