Using keys to sign posts is brilliant.

You can be in any country and "sign up" to use Nostr. It's hard to let go of the old nomenclature. You don't sign up for Nostr, you just use a private/public key pair.

With that said, if you believe your device is compromised, and want to change key pairs, but still keep the same “account,” that's not possible now as I understand it. Would love to see some sort of key management abilities in the future.