Have you ever stabbed someone over someone you love?
Bloody hell no. One must be insane to do things like that.
Knives are bloody serious thing, and there is no reason to use them in fight if your life is not at stake. My father liked knives a lot (and I do too). It was okay for him if I fought with fists (or kicks) with other guys, but I think he would give me hell if I ever used knife against anyone unless my life was threatened.
Once a guy, a student of the same faculty wanted to fight me, I think because he thought we both loved same girl (she told me she won't be with me earlier, and I finally accepted). I didn't protest much. We both were drunk (me less than him). But it was a civilized fight. We put on boxing gloves and started on signal, with a few other students watching. As I was more heavyweight and trained a bit in boxing, I put him down in two or three punches, and the fight was finished. No serious injuries for anyone.
But in general fights are not any good solution to love matters.