In downvoting discussions, the top post will represent the consensus of the people engaged in the discussion. Note that this isn't "the truth" or "the consensus of the community" but of the people engaged on the subject. For example, if you see an otherwise-liberal community discussing gun-rights, the gun owners within that community will flood in and are highly motivated on the subject, and so the consensus will reflect their interest in the subject.
But either way, consensus.
Without the downvotes, the top post is often misinformation or just trash. Because a small, motivated group pushes it up, and the rest of the participants can only argue against it but not drive it back down... this creates the "engagement-based content" that aggregators crave.
The problem, of course, is that bots and sockpuppets are treated the same as established community members and can skew the "consensus". Realistically, the leadership of an online community needs to be able to identify who are credible voices on a subject and give them the power to steer the conversation. Yes, it's not egalitarian, but these systems never have been.