To be honest, if they completely eliminated those remarks from Belethor, I would find the game to be a bit poorer because of it.
They were highly annoying when repeated at each encounter, but coming out just occasionally, and relatively seldom at that, they would kind of be in line with his character.
I actually wonder, if the civil war, which does adjust some merchant dialogue once the battle of Whiterun is over, could also have a hand in this. I couldn't tell, because I have only one playthrough, which is currently pretty close to being complete.
Maybe he realized you weren't interested in the trade.

Well, he doesn't actually have a sister, or so he claims, but at any rate I never saw one, so I wouldn't really know about that.
