I'm glad you felt compelled to participate. I really enjoyed that post of yours.
Like I said, under linear reward, even if we downvote everyone who doesn't engage in proof-of-brain, then all the reward are returned to the pool for other abusers to take.
Pushing this logic to its limit, 50% of stake will down vote 50% of the rest and the pool will still be full and the pool control by dust accounts.
Sure it won't happen but the problem remains the same, it's infinitely less costly to abuse than it is to police. Create a bot, comment 10 times votes those 10 comments, hope nobody flags you. The more people do it the less chance of being single out and flagged.