While downvotes can drive people out of communities, I have to contrast what happens in no-downvote communities, where often the top commentary is, to be blunt,

While downvotes can drive people out of communities, I have to contrast what happens in no-downvote communities, where often the top commentary is, to be blunt, far worse because corrections can only exist in the form of responses (and so more engagement). Downvote-based systems are better at having the consensus viewpoint and quality content bubble to the top, at the expense of pummelling some of the dissenting views. Upvote-only systems seem to have worse stuff bubble to the top.