2. Downvotes in particular are too cheap. I think it'd be cool if a downvote were accompanied and weighted by a comment: for each downvote, you are prompted to also leave a comment explaining yourself. If your explanation is insufficient and downvoted too much, your downvote is discounted. You'd still get ideological misuse per point #1, but it might improve things.
This is not specific to politics, despite your framing. This happens all of the time on HN with technical topics, too.
Does it mean:
1. I don’t agree with you
2. Your post is spam
3. I don’t like you
4. You’re factually wrong
5. Your content made me upset or sad
6. This doesn’t contribute anything
All of these things are better served as a reply or not vote at all.
Karma doesn’t really give you much. When you see a post you’ve made get -n votes, what are you to think? Are you to change in some way?
Some different implementations of voting that I would like to see tested are:
1. upvote only. Let the bad stuff filter to the bottom.
2. gas. Assign a cost to upvoting or downvoting. Especially with downvoting and flagging. Require the user to really think about what they want to downvote. For example this cost might be: a point system of which you get limited number of points per time period, or more interestingly you loose an upvote for every downvote.
3. Back off times. One cannot mass cast votes.
4. Votes are public.
5. Downvoted require a comment.
You can't really have any kind of discussion forum with highly polarized groups.
For a roughly aligned group, it lets good comments rise to the surface, though doesn't guarantee all will rise.
I think more important is keeping a relatively aligned group, smaller number of people, and some benevolent dictatorship to keep out the riff raff.
It's a lot like democracy, it only really works when people mostly agree anyway.
Discussion that's rewarded tends towards groupthink or the opposite of groupthink, something like automatic gainsaying.