What would the server do? Just summarize info from relays?
Discussion
You could implement some of what you're talking about naively by inheriting moderation decisions from certain lists/pubkeys, but a more nuanced model with real social graph analysis becomes pretty computationally intensive pretty quick.
Can we do that as a service? Users subscribe to pub keys that provide the analysis and return a new Nostr event type to the app. We have a similar thing for Feed recommendations here: https://github.com/nostr-protocol/nips/pull/493
Yeah, I think so. Either that, or via custom relays.