If only distributed signatures included trust levels -- then you could at least attempt something like that. Though unfortunately trust levels are themselves in

If only distributed signatures included trust levels -- then you could at least attempt something like that. Though unfortunately trust levels are themselves incredibly coarse and subjectively determined (does "I trust fully" mean "I checked 6 forms of government ID" or "I know this person by their handle"?). To be honest, I think Keybase has the only workable solution to this problem for modern online personalities -- tie it to directly to your other identities online such that you would need to break into many accounts in order to fake someone's identity. And individual users can decide for themselves what threshold of trust they have for someone.