The philosophy of Nostr and that of Bitcoin, however, are quite different.

In the case of Bitcoin, consistency is key, while with Nostr the philosophy is that each does what one wants. Bitcoin relies on economic incentives, while much of the Nostr ecosystem is maintained by volunteers who want to promote free speech, often even at an economical loss.

I have seen that post before.

Nostr events can be trivially collected, even across relays. One could make a dump of basically every reachable event. It would easily fit on a USB stick. That dump could then be uploaded through BitTorrent and, because Nostr events are signed, it would be the same as having all posts permanently on chain. So if that's unwise, so is Nostr.

You should assume someone will do this.

Nostr events aren't on a blockchain, but blockchains aren't the only way to store and share something permanently, as long as there is interest. Nostr messages, except for encrypted private ones, are publicly and permanently recorded as plaintext for everyone to see.

Now, I don't know if Satoshi here was talking about private messages or public posts (which can also be referred to as "messages"), such as Nostr notes. But assume public notes will be archived and forever provably associated to your public key.

I happen to see the archivability of Nostr as a feature.