The follow up questions:

Is the post on relay traceable and immutable? If so, how to prove and what mechanism is used?

Because on NOSTR, if the users want to get some information, they have to subscribe the particular relays first. If users don't follow some relays, the information can be missed. However on the Blockchain, all blocks can communicate with each other so it has traceability and transparency. nostr:note1kwxxjnl7qt2c6m53qde6r85gfqcvtqydchn8a847rpm69cf23ayqgyst4y