Nostr messages are all signed though. Why would you want two signatures on a message. And if two signatures are better than one, why not 3 signatures?
And GCM does not ‘add’ a signature per se.
> And GCM does not ‘add’ a signature per se.
Your own comment to which I replied said "It’s not tamper proof, ie signed, unlike GCM". Wouldn't most people consider something "signed" as having a signature?