Spammer will just spin up their own nip5, while majority of users without a nostr address are cut out from conversation. This is a win for the spammer. 

The default nostr experience should not be “you have to register an address to get your word out”. This is excessive and unnecessary when a client can simply show you notes only within your network (also requires users to follow others, and not an idea solution on its own). I don’t know what the best solution looks like yet, but if we enable something like “join with friends” where you automatically follow some suggested (by your referrer) users, wot starts working for you. 

Nip5 filtering would work fine for something like Ditto.