Wasn't Karkat's whole deal that he wanted Terezi "in all quadrants" so he could have her exclusively? And how his romantic inclinations was a callback to the Signless and Disciple? Saying he doesn't feel the same way towards Dave as he did towards Terezi is a little. Uhm. Extremely unfortunate.

One of Karkat’s big struggles with Quadrants is that he struggles with them in the same way people struggle with Queerness- Except instead of being orientation-related, it’s about the different kinds of Romance. When he is with Dave, he does transcend Quadrants just like the Signless- Because their relationship is a Human Relationship. The ambiguity of their Quadrant mentioned by Vriska and the fact Dave himself doesn’t really get Quadrants too much are big hints towards the fact they’re together, not as Matesprits, not as anything other, than the repulsive and alien emotion of Human Love. Now adding a Poly Human Relationship on top of this is an entirely different can of worms, because he wouldn’t be obsessively switching Quadrants or planning things, he’d just Love two people.

Not to say, are you trying to imply Karkat wanting Terezi in all Quadrants was at all healthy? Because that and Dave’s relationship with him most definitely have little in common.