I would prefer(at least for a quicker solution) the need to make a minimal 127 character reply to the downvoted post so in order to be able to downvote. It doesn't need to completely remove the "separate mana" for downvote, but it would obligate the downvoter to make a statement before casting the downvote, even it is pasted auto-text or completely gibberish of random characters.
That way the community could at least have access to the downvoter's reasons to do so and, if it's the case, counter it with their own upvotes.
I would prefer that also, that in order to down vote you must state a reason. For some reason though people do not want to have a mandatory comment of any kind. They always point out a comment is not need to up vote so why one to down vote. They do not see the difference in an up vote being a positive action, and a down vote as being a negative action. No society I know of has ever required justification for an individuals positive actions, only their negative actions. The people that do not want a comment or the ability to give the down voter themselves a down vote are the one that think down votes are a positive action. They are not the are a negative action and a control action.