I’m not trying to be an arrogant ass correcting you, but I think your answer is a good starting point.

but rather a web framework, kind of like Lemmy

To extrapolate a bit, any platform is going to have a protocol (lemmy uses ActivityPub), servers, and clients. Their site says nostr is the protocol, and there’s relays (servers) and clients that communicate using the nostr protocol.

it operates not so much like blockchain, but more like Tor/onion networks

I don’t think that’s quite right. The protocol itself does not encrypt the content of messages (althrough there’s no reason you couldn’t send encrypted content). The crypto stuff in this case just “signs” the content allowing everyone to verify that the message came from the purported author and hasn’t been edited.

If you have a private key, a public key, and a message, then you can use those three things to compute a signature.

If you have a signature, a public key, and a message, then you can confirm whether they match.

Therefore, only the person with a private key can author messages, and everyone with the public key can confirm that they are the author.

So in some ways you could say, your private key is like your own account or identity, and the public keys you keep track of are the accounts of your friends.

The “federation” methodology is interesting too. Relays don’t sync, they just store events from those clients which are connected to them.

In summary, as you said, it might be interesting for people that are worried about being “cancelled” or censored. On this platform it would not be possible to purge or alter someone’s messages, unless of course you got their private key.

It makes me a bit worrisome about the risks a relay operator would be taking on

I agree. I wouldn’t want to run a relay open to public signups. Conceivably if I had anything worth saying I might run a private relay just for myself or direct contacts.