Which doesn't make much sense since all MLS communication on WhiteNoise is wrapped and encrypted again. But maybe I am wrong.
Discussion
from ip address? idk
If a Nostr relay requires AUTH—as based on a paid subscription—it would be one way a pubkey/npub could be associated with a group ID (the only metadata available, afaik). The other would be based on an IP, but that is similar to Signal et al (and mitigated with VPNs and etc). E-cash 'blind signatures' seem to be the best solution for relay 'subscriptions' without knowledge of a pubkey. It was designed for this scenario, even if from 1981.
Unrelated, but your client hasn’t published the event to my inbox relays.
Because sending addresses are decoupled from IDs and constantly change, a message relay cannot reliably infer who is in the group.