Downvote system HN

When you don't like a comment on HN you just don't change the points of the comment. When you really think a comment is out of place you downvote a comment.

This is a great system. It keeps HN clean from flamebates an other spam.

Today my comment was downvoted. That's ok. I won't complain about that. Only this time I was very curious about the reason.

I like to be curious because I like to learn. And one of the best way's to learn is by your mistakes.

So wouldn't it be great when a downvoter must apply a simple explanation? Or could this lead to discussions about the explanation instead of the subject?

edit Changes 'posts' to 'comments'