Fill-Side Non-Retail Trading on Polymarket: Identification Limits, Behavioral Tiers, and Microstructure Signatures

This paper studies behavioral concentration in Polymarket's public executed-fill record and formalizes what that record can and cannot identify. A pre-publication reconciliation corrects the empirical scope to the legacy CTF Exchange over Polygon blocks 86,008,447–86,107,178, containing 13,356,931 OrderFilled records, 77,204 addresses with at least five attributed records, and 43,116 token identifiers; negative-risk markets are absent. The archived feature construction credits both maker and taker addresses and is not invariant to match fragmentation. Two results remain durable: public fills do not identify the quote lifecycle needed to infer market making, spoofing, or strategic withdrawal; and a one-cluster result rejects density separation in an observed feature space, not latent economic heterogeneity. A match-normalized, mint-aware, multi-window replication is required before treating cohort shares as stable venue properties.