Nostr: How does moderation work without one central operator?

Short answer

Different clients, relays, and groups can make their own choices. A client may hide muted accounts; a relay may refuse or remove events; a group may enforce membership and posting rules. Those decisions affect the surfaces they control, not every copy of an event. This offers user choice but can also mean different people see different feeds and moderation outcomes.

Sources

NIP-51: Lists, NIP-29: Relay-based groups, NIP-11: Relay metadata.