What it catches
A signature proves a record was not altered. It says nothing about what a registry chose not to serve, or whether it served the same answer to everyone. Corroboration across registries catches the three ways a registry lies.
A record was hidden
One registry serves an agent that another registry confirms absent. A single caller cannot tell a hidden record from a record that never existed; two registries can.
An endpoint was forged
Registries claim different addresses for the same agent. The unsigned endpoint a caller would connect to disagrees across sources — one of them was substituted.
Different answers to different callers
A registry serves one identity here and a different valid one there — across callers or across vantages. Its own answers, compared, contradict each other.
The verdict. A sweep resolves to AGREE (the decisive sources
concur), DIVERGENT (they disagree — a finding is raised), or
INSUFFICIENT (fewer than two decisive claims to compare). An unreachable registry
is never mistaken for one that says a record is absent.
Out of scope. The Quilt does not judge whether an agent is trustworthy, capable, or well-behaved — only whether the registries that describe it agree. It attests the consensus about a subject, not the subject's merit.