Looks like we're starting to get fake accounts like Jack@primal.net on Nostr, but that's defrayed by the trust gained by Jack's main account. A sophisticated attacker might spawn accounts that aren't on the platform already, making things difficult to track. Right now, Nostr's verification process is longest-standing npub with most followers, but perhaps, in time, there should be tracking on people who zap back and forth as "verification". This has the incidental benefit of getting people to use Bitcoin/LN even if they're not Bitcoiners.