I think upvotes and downvotes should be harder to do.
An example of what would make a vote "harder" would be to require reason-words. When you click down-arrow a box might pop up where you must select (or better still, type out in full) at least two words justifying the vote such as "Abusive" or "Pointless". This would also help to prevent fat-fingered downvotes that I've accidentally done on my iPad because the arrows are too close together and irreversible.
I don't think making it mandatory is necessarily a good idea. But I would love to be able to have people give me a short reason for an down vote so that I can hopefully see what I'm doing wrong. Anonymously of course.
One issue I could see happening would be people abusing the feature to send hateful messages. Some solutions may be to allow users to delete messages or block the ability to give them text feedback along with a down or up vote.
Another problem might be causing a sort of hugfest where users try to get upvotes by upvoting someone else, creating an upvote ring. (Eg: Including their name in the feedback and asking for upvotes.) One countermeasure would be to block the user from putting in their unabridged unedited name into the feedback box. (Of course, this could be circumvented in the way that almost all other online censor systems are circumvented. Obfuscation.)
Yes, an open text channel could be abused and it is only unlikely to be abused if it's public; e.g. everything reads "makecheck said X" and not just "X".
Maybe the right thing is for downvotes to always list voter IDs (but probably not long upvote lists). If I downvote something for "the right reasons" I don't really care if anyone knows it because I expect most people will agree with me. The opposite would be true for someone doing a lot of petty downvoting; he or she would probably be embarrassed and discouraged once everyone can see that the same person has downvoted a bunch of comments for no reason.
One way to find a "reason" for a personal downvote, then, would be to look at everything else your downvoters have downvoted. One of two patterns would probably form: either these people are in the habit of downvoting lots of stuff for no reason, or they seem to be downvoting comments that have common themes.
Along similar lines, I wondered whether making up votes have a steadily decreasing effect (say, first up vote is 5 points, then 2.5, then 1.25) and down votes have a steadily increasing effect (0.375, 0.75, 1.25...) would be wise.
An example of what would make a vote "harder" would be to require reason-words. When you click down-arrow a box might pop up where you must select (or better still, type out in full) at least two words justifying the vote such as "Abusive" or "Pointless". This would also help to prevent fat-fingered downvotes that I've accidentally done on my iPad because the arrows are too close together and irreversible.