The main differentiation that I can think of is the relays. Right now the entire network is a level playing field. We can connect to any single relay, and if that relay is connected to the rest of the network, messages get shared with anyone who has included that relay on their list, but they can't see which one it was posted on. Perhaps an optional notation that gives a tag for the relay would help build a community minded view of Nostr.
It would also be possible to do the opposite, design relay software to be exclusive on which profiles can become a member, and also design a client to restrict access to only a few or even a single relay. That would be a secure place for people to communicate with no way for anyone else to get access to it. I wouldn't be surprised if these were already in existence.