One thing I find interesting about my own highly ranked comments (and, I suspect, a lot of the lower ranked ones too) is how many of them reference books or articles that elaborate in much more detail on the subject. The rest tend to rely on my personal experiences and domain knowledge. I don't think this is a coincidence: a lot of the best comments exploit some kind of information asymmetry, where the writer knows something or knows about things that most don't and hence has a lot to contribute.
(Exception to my general rule above: this comment).
