How does Fedi know which PeerBadges to trust?

The Manifold integration inside the Fedi app carries its own list of Signers it trusts, and a badge only counts inside the app if one of them signed it.

Anyone can sign a PeerBadge for anyone – that is how an open protocol works. So a PeerBadge on its own does not tell you much. What gives it weight is who signed it, and whether the app you are looking at it in recognises that Signer.

Currently the Fedi app trusts a small set of Signers at Fedi. When the app checks a Manifold guardian before a federation is formed, what it is checking for is a badge signed by one of them. That is what the Fedi verification on a guardian means.

Keep in mind that there is no special Fedi version of PeerBadge. Fedi's app runs the same protocol any other app would, and the only thing that differs between one app and another is the list of Signers each chooses to trust. A different app could trust an entirely different set and reach a different conclusion about the very same badge.