That would be an interesting experiment. Make it a 2D axis... Agree <--> Disagree, and Low Quality <--> High Quality. Only allow voting on one of the options.
... left and right vote in addition to up and downvote?
Do not specify any rules nor instructions about when to vote left and when to vote right, but too much votes in either direction and the comment starts getting hidden.
If you disagree with the trend where any particular comment is going, figure out the horizontal direction you should click by yourself.
edit.
I think there is no need for up/downvotes after this system is implemented. Some secret amount of horizontal votes in either direction is good (counted as upvote). Too much over the limit and the extra is counted as a downvote. Hide the score from voters. Ban comments that attempt to discuss the score of any comment. Now everyone has a reason to be a bit more careful when voting (...except when a comment is obviously too left or right).
There are some opensource, reddit alternatives that might be willing to implement this. https://lemmy.ml/ comes to mind. You could suggest it there and it might fall upon open ears.