I sort of view Karl as someone that represents one of the less obvious reasons why the Circle was so terrible. He seems to be a good guy (we don’t really know him that well, but…he does seem to be several things that are pleasant and Anders says as much) and perhaps he and Anders could have fallen in love if he had gotten out before being made tranquil (assuming he didn’t freak out about Justice). But ultimately, he was a good guy whom Anders clearly respected and, at one point, had a physical relationship with. But because of the Circle, they could not allow themselves to fall in love.
I mean…that’s tragic. Love is amazing, yet mages deny themselves the joy because it’s dangerous to love someone, to openly care for the existence of another human being because the templars would use that emotion against them.
Given that Anders stresses how long it’s been since they were together and the fact that he gets over Karl’s death so quickly, I’m going to believe him when he says that he’s never known a mage who fell in love before and be all wibbly over how mages are punished for their very humanity in such a way that two people who might have had something special weren’t able to have much of anything.
Do people say that Karl and Anders were in love? For me, the attraction of that pairing is the tragedy of the almost-love, could-have-been-but-never-really-was dynamic.