I think civil and honest discussion would be better served without the anonymous down-votes. One can still retain privacy with a pseudonym.
I find it ironic that Hacker News is not Hackable! The most important thing about HN, its ranking algorithm and reputation system (karma), is closed and not hackable in any way. I know HN wishes it could come up with a better algorithm, and even pg wrote about the need and how HN will need to evolve (I can't find that post of his right now). What better way to come up with a better way than to let its userbase of hackers hack away at it? If the API exposed votes, there would be a blossoming of alternate front pages and comment rankings.