[kbenson]

I wonder how much of the karma for the insubstantial stuff is actually a response to not being able to down vote.

When you can't down vote, seeing a reply that sheds new light, puts some of the ridiculousness in context, or just takes a person down a notch may get a vote because it's your best way of voting by proxy.

For the comment writer it's a bit of a double edged sword. Sometimes the feedback you get relative to the time and effort put into a post can be disheartening.