It's not exclusive to HN, pretty much any site with a negative voting system gets used purely for disagreement rather than 'this is bad content'. It's especial

It's not exclusive to HN, pretty much any site with a negative voting system gets used purely for disagreement rather than 'this is bad content'. It's especially prevalent on Reddit, where you will quite often see words to the effect of "downvotes are not meant for comments you disagree with" The only-allow-upvoting thing is something that Facebook has been doing forever. Now that they're added a dislike button, they will almost certainly fall into the same traps as other sites like HN and Reddit.