One question I ask myself now before commenting is: Will this comment significantly improve this conversation? I try not to comment if the comment is merely: 1. clever and amusing 2. expressing anger/disagreement 3. disproving a wrong but unimportant claim made by another commenter. Besides these, submitting, upvoting, downvoting, not voting and flagging are enough to make HN more interesting for myself.
I may have good intentions to begin with, but if what I say reads as being one of the three points you wrote, there's no point in having other people argue against my invalid or ignorant claim. It just leads to semantical flame wars.