I’m not a dev or a tech expert, but the decentralized nature of a protocol (in this case #nostr) where it is run in many distributed #relays (databases), makes it difficult to get censored/banned. You’d have to take all the relays down at the same time to hurt it; that’s the whole point, that’s the power of decentralization.

Regarding the IP address, I don’t know if relays store it. And an #nsec for every post would be impractical imo.