It may not even be official corporate manipulation. HN is frequented by a lot of industry insiders, and if they see something that doesn't resonate with what they know to be true they'll downvote.
Exactly: there's a ton of people here who work at the big ad-tech companies, so of course they're going to downvote anything that promotes ad-blocking since that harms their own paycheck in a way.
Imagine a discussion forum for medical topics (science, research, etc.) where 1/3 the users work for companies that sell homeopathic "remedies", and how that would influence moderation there.
