"If their time really is worth so little, they probably can't produce karma-worthy comments anyway."

I can throw out a quick comment in 2 minutes. I enjoy writing quick comments, because I like talking about myself. I expect a lot of people like talking about themselves, given various social conventions and media presentations.

I almost never see a comment of mine voted down unless it's actively disagreeable (BTW, cryonics is a scam!), attempting to appeal to humour (you lot seriously cannot take a joke), or actively insulting (I like my karma enough not to give an example :P)

I'd idly estimate that I average about +1 karma per post. Basically, they're a waste of time.

I have over 1,000 karma.

So, the community consensus is that I'm a worthwhile contributor, despite the vast majority of my comments being more or less a waste of time. Specifically, I'm worthwhile because I'm prolific.

(Of course, if I cared about milking karma, I'd put this time in to writing a couple well-researched main posts and earn 100+ karma from an hour of work, instead of ~30/hour contributing a two-line comment here and there.)