I did think of one problem, though I like this idea and resteemed the post.

It would require a limit of one dissenting comment per user. Otherwise a person could create multiple dissenting comments and up vote all of them which would become a force magnifier.

This actually could still be done with the collusion we see going on.

Whale A creates dissenting comment A and up votes it
Whale B creates dissenting comment B and up votes it AND A
Whale A also up votes B.

Perhaps a way to only allow a single vote of yours to be applied to a dissenting comment, so if you wish to put your dissenting vote on dissenting comment B and you already voted for A then you have to remove your vote from A first.