What I do, if I see a greyish comment on HN, and it's obvious that the opinion/idea expressed is being downvoted by groupthink, I upvote it. Even if I don't agree with the comment. Mostly because I don't believe ignoring/burying those whom you disagree with as solving anything. My choice of doing this is more of a means than an end. It's odd how narrow-minded and self-reinforcing a group of out-of-the-box free thinkers can be, especially out here. I can't impose open-mindedness on the masses, but I can try to at least help the voices of the dissenters remain visible.
Maybe showing the text "Some disagree with this", if some people disagree? Or "Many people", if many. I linked to a demo about how that can look, in another comment here — search for "Look, a demo" on this page.
I've thought about the transparency bit before. I guess keeping it opaque has the effect that you can't have a vendetta for someone who down-voted you and in general the down-voters has had to acquire enough karma to get the privilege in the first place, so we hope we can trust them.
Showing more detailed voting stats is something I hadn't considered. It does seem like an step forward and it doesn't seem to pose any danger as far as upsetting the ecosystem that has been built.
In general, I'd like to see voting and flagging on HN become more transparent. While there are some good arguments for maintaining the current "anonymous" approach, I testing some alternatives could lead to something better.
One quick change that I'd like to see would be to privatly expose the total vote count to the poster instead of just the net total. As it is, it's hard to distinguish a contentious issue from one that only a small number of people are interested in.
For example, instead of showing a comment as "-2", it might show "-2" with a mouseover that shows "+20 -18 = 2". This would be a tiny change, the data is already being recorded, and it could just as easily be rolled back if it doesn't produce a desired effect.