> I was thinking more about it more as just measure for anti-spam and limiting bots It won't help with that at all, since without requiring active involvement

> I was thinking more about it more as just measure for anti-spam and limiting bots It won't help with that at all, since without requiring active involvement of some credential or trusted party, all there is is a static signature saying "there's a person called $name born on $dob", but nothing saying "and that person wants to <send an email|register an account|...>". There is a way to use ICAO documents supporting "Active Authentication" in such a way, and I've seen proofs of concept leveraging it, but it was an unintentional consequence of using RSA signatures for authentication and fixed/removed in newer cards.