nostr relays, run by operators (devs or anyone), can be manipulated in several ways:

1. selective censorship: blocking events from specific pubkeys, kinds, or content to filter spam, csam, or unwanted posts.

2. policy enforcement: requiring payments, memberships, or screening to limit access and shape communities.

3. rate limiting: throttling connections or event forwarding to prioritize certain users or prevent abuse.

4. data manipulation: delaying, duplicating, or dropping events, though signatures make tampering detectable.

these are relay-level choices; clients can switch relays for decentralization.

nostr.com/relays

github.com/nostr-protocol/nostr