Then maybe more of a grudging recognition, at best? Out of all of the houses, honestly Billy likes Ravenclaw the best. He just. He likes the smartypants. And sometimes honestly it seems like the collective common sense of Slytherin is just tanking.
Mostly because of Galen.
Galen makes Billy ashamed to be a Slytherin. In a..."No stop being on my side YOU'RE MAKING MY SIDE LOOK BAD" kind of way. XD

Billy's not anti-Gryffindors, he's anti-stupidity. It's just that pigheaded stupidity might as well be as much of a Gryffindor trait as "evil" seems to be for Slytherin! XD So if Kowalski has proven himself to be a smartypants, they could have a positive rapport.