Very interesting. Much to be made of it. Any thoughts on this line? It's really the turning point (other than Marc's song at dinner). Although something clearly happens with Bartel after the song is sung, he still is calling him "Marc" outside - until after he says this line.
i think the line is pretty simple...in my opinion this is the point where "marc" turns into "gloria" to bartel. bartel says "why leave if you came back"....meaning, why did you leave me in the first place, if you were just going to come back...thats the way i took it, in bartels mind Gloria (marc) has come back to him, after leaving him for however long that it was. so he was just asking why did you leave me if you were going to come back to me. in other words, why did you make me suffer thinking that you had left for good.