Solutions are:
1) trust graph (accounts followed by people i follow and they people they follow, all the way up)
2) some significant cost for new users (which could be proof of bitcoin paid or owned, or proof of work in creating an account or for posting a message)
quoting note1zfh…cdwxIf this is working I shouldn't see any reply guys in my own client beep boop test wss://nostr.oxtr.dev