I've noticed that top comments on HN are frequently meta (about the article's writing or author, not the article content) or flat-out disagree with it more often than on Slashdot. Readers here also tend to actually RTFA much more often before commenting.
That's not necessarily a bad thing. If you read the article and have nothing to add, then best say nothing. Better than saying something about an article you haven't read, that's for sure.
