Pattern matching is a game of wack a mole. The spammers are already evolving. Eventually this will be AI spam on a freshly minted npub. It will look like any new user. Nostr apps will either be forced to block new users or implement something radical. 

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) nostr:note1zfhwgmkwtx48jtmzyrs9jaq82tm58grp45slxcvlc2n5atq8u07s80cdwx