Since people are comparing Nostr to Bitcoin today, because both are decentralized:

No they are not the same thing, not even close. The big difference is th entire concept of a ledger.

With bitcoin, the ledger guarantees no transaction, once accepted into a block, can ever be deleted.

Nostr has no such guarantee. While relaysay choose to keep notes indefinitely, there is no reason they should keep all events forever. There is no expectation that the decentralized network of Nostr will save your precious little note for any specific duration. Nostr is NOT where I would put something I never want deleted, forgotten, removed.

Having no control over the storage of data had always been the true nature of things, until we had the bitcoin ledger/timechain. Nostr may just be helping us to come to grips with that reality, and learn how to live with the knowledge that your contribution may last decades, or may be deleted tomorrow, and there's little you can do about it.

Could you run Nostr on a timechain with a ledger of all notes? Sure, it could be done, but you would have to pay for the privilege of storing each note, and the transaction volume limitations would also be prohibitive. But would you even want guaranteed storage of notes?

We already have it anyway, through OP_RETURN.