Right. I attempted to argue that this was because the comment they disagreed with failed to make them stop and think about why disagreement exists, and re-evalu

Right. I attempted to argue that this was because the comment they disagreed with failed to make them stop and think about why disagreement exists, and re-evaluate their position. That is, downvotes are generally a sign of failure. Certainly, some people stop, think, disagree, and downvote. I believe that this is the case when the original comment is sloppy, and generally warrants a reply. In some cases, especially various kinds of politics, the replies are omitted presumably because of fatigue. Such people have already replied to the argument enough times in their life to not want to do it again. That could be interpreted as a failure of domain research on the part of the original commenter, but I don't like to blame people for not being "well-read".