Reason for downvoting?
(Also sshhhhh, it is anti-HN to discuss downvotes)
I believe however that this is one of the fundamental flaws of Reddit-style websites. On an imageboard you are obliged to make your disagreement in words, constructive or otherwise. Here, you can passive aggressively click the downvote button and leave the post in limbo.
(I am not at all talking about the present case, let it be clear :-) )