The world would be a very dull place if we all had the same opinion.
If you are getting downvoted occasionally then there is not much to bother its part of life. There will always be ones who disagree. But adding comments to downvote will be piling up mess upon mess.
in case you got downvoted and you didnt mean to be a trouble maker, lets ignore and live happily together. In the end is HN a place where one seeks appraisals alone?
To help enforce good comments :)
Adding comments to downvotes would be a DISASTER.
It would mean that you would suffer through huge amounts of dumb comments before you would be able to tell the quality ones.
Yes, downvoting exists to increase the signal-to-noise ratio, and adding more weight of comments attached to a low-value one does the opposite.
Showing the karma score promoted nasty back-and-forths that would get the moderator dragged into it as people tried to score more points. So that isn't something the mods want on this forum. But not having any way to tell comments with a positive score from those with a negative would also be problematic.
I understand the frustration and the desire for some kind of constructive feedback. But as someone who does, at times, give people my opinion of what went wrong with their comment, more often than not, it doesn't help them and just comes back to bite me.
Downvotes on HN are kind of like democracy: The worst system ever -- except for all the others.