just as a community crafting thought, i'd like to see two types of flags, one that is for fact (for lack of a better word) and the other is for opinion.
so, the idea would be that you can use the factual up/down to keep spam or garbage posts in check and punish/reward the submitter for quality posts. and you can use the opinion one to up/down vote a comment based on how you agree with it, and it doesn't affect the submitter (and maybe helps suggest things for you). just something i've been thinking about lately.
I've thought about that too. But --- on top of the usability issues --- if people are misusing the current up/down voting control, why would they correctly use a dual up/down voting control? What's the incentive for people not to mark comments they disagree with on a point of opinion as being factually wrong?
it won't inherently stop anyone, no, but it would give someone a decision point before they vote, instead of just clicking the down button for the comment making them grumpy. they'd have to make the choice, which is not an option now.
plus, an opinion vote would tie into other features, so it would behoove someone to use it properly.
Of course, people confuse fact and opinion all the time, particularly when they have a bias about something. Even where there's not confusion, "fact" downvotes would certainly be abused.
the hope would be that they would be abused less often, especially if opinion were tied into features.