That is exactly the part I keep thinking about. Different Nostr clients often connect to different sets of relays, so portable reputation would not happen automatically. A review might still exist somewhere on Nostr, but a new client has to know where to find it. NIP 65 can help by advertising the relays a user normally reads from and writes to, but the reputation events themselves would still need a common format and enough replication across relays. If Lumen gets that part right, a tutor's reputation could potentially survive even if the original application disappears. That would be a very powerful use of Nostr.