This used to upset me, I have simply stopped caring and feel much better for it.

That said, I've had some fairly drastic changes in my private situation so I'm not nearly as active on HN as I have been in the past.

The best way to deal with an unjustly downvoted comment is to simply vote it up if you come across it (this you can do pretty much forever), and to ignore the issue if it happens to you on the assumption that on balance HN contains more nice people that griefers.