The only voting site I use is HN and here, a good number of the people who down vote will also comment. That HN hides the votes of each post is useful because

The only voting site I use is HN and here, a good number of the people who down vote will also comment. That HN hides the votes of each post is useful because you only wind-up with a vague guess as to how other posts are received. I suspect that not offering down votes would not make people more likely to comment. I will vote and then comment to reinforce my vote.