I second this, I find sdegutis's comments to be very useful, if only to provide a fresh (and entirely valid) perspective. Contrast is so so needed in our community...
I have "showdead" turned on in my HN profile purely to be able to read constructive comments that have been downvoted to death. I agree with others in this thread that there isn't enough variety of opinion in many discussions on HN, and I'm of the opinion that if you are polite, and especially, if you are erudite (as you seem to be) you are most welcome.
I'm saving my downvotes for those who are rude or insulting to others.
The result of downvoting is not simply a karma thing. It actually effects visibility of comments. Downvoted comments do not get any discussion.
Therefore, writing a comment that gets downvoted is a one-way communication channel. There's no benefit in it for me when there is no discussion.
My time is too precious to give away for free. Your time is too precious to waste reading downvoted comments.
So it's in everyone's best interest for people who don't share popular opinion to stop commenting.
That includes me.