While I really like this kind of articles I don't like the search for single or few causes of intelligence or creativity. Happily human beings and the world in general is more complex and trying to absolutely follow what these studies say is a bad idea.
People who downvote without adding a reply...
Subsequent comments bringing up solely the issue of being downvoted are being downvoted on sight, because those sorts of comments are never constructive to the discussion and are disfavored by the site guidelines.
http://ycombinator.com/newsguidelines.html
"Resist complaining about being downmodded. It never does any good, and it makes boring reading."
By the way, the premise is false that there is any rule here against downvoting without commenting. Implicitly, some comments should be downvoted on sight.
http://ycombinator.com/newswelcome.html
"Essentially there are two rules here: don't post or upvote crap links, and don't be rude or dumb in comment threads."
The site founder has commented that downvotes for disagreement are permitted here.
(In order of time of posting, with the last post quite recent.)
"I think it's ok to use the up and down arrows to express agreement. Obviously the uparrows aren't only for applauding politeness, so it seems reasonable that the downarrows aren't only for booing rudeness."
https://news.ycombinator.com/item?id=117171
"IIRC we first had this conversation about a month after launch. Downvotes have always been used to express disagreement."
http://news.ycombinator.com/item?id=658691
"I sometimes downvote things that seem mistaken. I think most users do."
https://news.ycombinator.com/item?id=1006808
"If there's one thing I wish I could do to improve HN, it would be to detect this sort of middlebrow dismissal algorithmically.
. . . .
"The problem with the middlebrow dismissal is that it's a magnet for upvotes. The 'U R a fag's get downvoted and end up at the bottom of the page where they cause little trouble. But this sort of comment rises to the top. Things have now gotten to the stage where I flinch slightly as I click on the 'comments' link, bracing myself for the dismissive comment I know will be waiting for me at the top of the page."