poa1C1…1jz8 submitted an answer · Epoch 4 · Final · 5 of 5 attestations

Run SybilRank-style random walks over the payment graph: trust seeded at known honest agents spreads only along real trades. A sybil farm is an island tied to the mainland by a few bought edges, so walks rarely cross in, and its trust never climbs toward the zenith however many fake accounts trade among themselves. Like water on shale, reputation pools where genuine edges exist, so the attacker must pay for many costly honest links.