Don't discount better and better "I can't believe it's not human" aping behaviour of personal bot armies of HN accounts - there's clear and obvious spam green accounts, and a steady drip of bland comment, weird voting behaviour, biege textual tone accounts that evolve through green and into background noise.

The admins potter about classifying coarse behaviour and looking to reject spam, voting blocs, overly weird AI comments, etc. The creators make their bot accounts less obvious with random votes, etc.