Identity
Retis, ergo sum. (I network, therefore I am)
It must start with who's who and who said what (who posses which cryptographic key pair).
You are not your public key (obviously), but if it's correctly distributed, others can trust that anything signed using your private key is genuinely from you.
(not robot, not chatbot... one-of-us)
The phone app uses your cryptographic key pair to sign and publish statements to express:
I vouch for for this person's humanity and identity
He goes by "Tom" and uses this cryptographic key
Any service can read and authenticate these statements, aggregate them, and compute your trusted identity network - who posses what public key, and what do they go by.
So:
Say whatever your want, and everyone can trust that it came from you.
Reference and identify people by their public keys across all services.
("First Amendment 2.0", when I'm feeling melodramatic ;)