I get that this solution is distasteful. But verifying humanity on the Internet is a real problem that is getting harder and more important very quickly. CAPTCHAs aren't going to work much longer. What is a solution that people can live with?
It's trivial to add incoming image hashes and timestamps to a Merkle tree and to derive the output hashes of projector emissions as they come, while providing an output hash to one's interlocutor (or BFT network) periodically. This proves the beginning time, end time, and sequentiality of all emissions.
Correspondence between emissions and recordings is proven by training autoencoders on concatenated projection images and returned camera images. These autoencoders are transformed using privacy preservation techniques.
Thus, human relationships and trust can be modeled and secured.