That's great, but I don't think it addresses the basic point: sharing edge names requires a way to share those names, and that's a trusted third party (one with a degree of centralization, to boot).

There are ways to (dis)intermediate that trust (like a PKI), but the shape of that PKI or other technique is itself a question of decentralization, security, etc. I think that's a very hard underlying problem that the petname design needs to at least offer some opinions on in order to make claims about security.

Yeah, this is one of the big issues with digital peer trust networks. Trust in human interactions is fuzzy and very conditional, which is hard to collect, represent, and update in a user friendly and low effort way. Hence we tend to collapse it to a single, often-binary, trust score.

I would also trust a mutual friend over a complete stranger. But that's not the point of the observation: the observation is that "trust" isn't a boolean, but an umbrella term for a wide range of policies that we apply to different principals.

Or in other words: transitive trust is a thing, but it's of a different color than "trust." Attempts to gloss over this in web-of-trust designs have historically not gone well.

I'd argue "friend of a friend" is strong transitivly because it's explicitly chosen by all parties involved.

Trust in a professional relation - a doctor, especially - is actually very strong, because of the professional requirements to be trustworthy, and the protections built into that (being held accountable by an organization and/or lawsuits).

"Family of friend" or "family of professional" isn't necessarily a strong relation for exactly the opposite reason, unless maybe the first-degree contract is vouching for the person.