[loganfrederick]

This is pure speculation, but I wonder if only providing an upvote button discourages positive comments, leaving only negative ones left to actually be posted. The purpose of the upvote is intended to mean "I support this contribution to the discussion", but is too often simply used as an "agreed" vote. There have been plenty of other related comment thread discussions along these lines as well.

[jonathanjaeger]

Maybe in part, but I think for the majority of people thinking positively about a situation results in a nodding of the head and moving on. Most don't find it interesting or adding to the conversation to just write, "I agree because of what you said or because of X, Y, and Z."

If you disagree, however, there is an emotional tendency to want to argue or lash out(especially under the guise of partial or full anonymity). Arguing makes for a more interesting read or prevents the 'yes' mentality.