Ahh...well... there's sort of moderation though.

Anyone can tag something as say, hate speech or nudity. Some nostr clients, like the one I use, will automatically block stuff that people I follow have already tagged as , but still give me the option to reveal the offending post if I really want to see it.

And tags like spammers, are automatically added to the client so they get ignored by default.

It's not perfect, but it does reduce the noise down to an acceptable minimum.