> I think it is reasonable to observe that the current PGP WoT is designed to try to unambiguously and unimpeachably map public keys to entities (if not necessarily literal human beings).

I don't really think the PGP WoT can "unambiguously and unimpeachably" provide that mapping, or is even intended to. At best, I think that the WoT documents trust relationships between entities with keypairs.

I actually really like this feature of the WoT, because I think it does a good job of simulating the actual trust relationships between people in real life. In a private conversation, I might imagine a friend vouching for someone another person as trustworthy; a key signature from my friend does something similar, in a secure fashion. This is good because I don't want my web of trust or social network to be able to say "this key is certain to be trustworthy": after all, it can't actually guarantee that. But I don't mind seeing trust opinions from my friends, and their friends' friends.

If anything, I think the trust relationships in GPG ("unknown", "marginal", "full") are too unclear, and I know that these numbers mean different things to different people. I'd prefer the ability to add a short note to the signature so I could say something like,

"I know this person well and you can be confident that this key is theirs, but I don't think they're careful enough to trust their signatures."