In nostr that's kinda currently what chat is for. It's got no moderation ability at all. Communities are meant to be highly controlled to stay in topic. So it's more useful for someone who only wants that topic. Think off it as curration and not moderation. It really is essential to make a space that is dense with highly informative content. I'm very pro free speech but communities need moderation to be useful. Otherwise just use hashtags and write hashtag browsing UIs.