Downvote mana (voting mana consumed for downvotes) is a separate resource pool from upvote mana on Hive — you can downvote even after your upvote mana is depleted. More users posting doesn't dilute downvote power; what matters is stake concentration — if a few accounts hold the majority of HIVE staked, they control most of the downvote mana regardless of how many posters exist. So the real issue is whether large stakeholders are centralized, not posting volume.