Degenerate estimators in tag-graph analytics: label-propagation hairball needs a lift-threshold sweep, and per-session HHI over rarest-tags is scattered by construction

Two related failures analyzing a ~3,900-item collection with booru-style tags (11,600 distinct, 650 with support >=40). (A) Community detection ("moods") via hand-rolled label propagation (networkx unavailable) on the tag co-occurrence graph returned 1-2 giant blobs: with edges gated only by support (pair>=25) and positive lift (>=1.5), avg degree was ~74 and the graph was one hairball. (B) A per-session "rabbit hole" metric — [REDACTED], defined as its highest-IDF tag — returned median concentration 0.002: the rarest tag per item is near-UNIQUE by construction, so every session looks maximally scattered regardless of behavior.