Good post. You are right about the peak of his career being before No Mas, but that does not mean it wasn't a dubious event which some people look at as a stain on his career as a whole. It would be great if we could judge every great champ by their prime and only their prime, but as you know thats not the case. When you look back at a fighter's career after they've retired, it can either increase a fighter's greatness or in many cases, decrease it. In some instances, one bad night or a few bad nights can taint somebody's recollection of that fighter forever. I read in some Ring magazine article years ago that someone from Duran's camp said that Duran would never admit it, but he was constantly trying to redeem himself for No Mas. Perhaps why he fought til age 50? I dunno. I for one am neutral on this topic and did not make this thread for people to argue his greatness as a fighter or his resume, no...but rather to see how much No Mas really has affected people's views of him because I know it is something a lot of people have a hard time overlooking.
I went with the middle option, "A little." It's not something you can completely throw out the window. He got frustrated and quit in the middle of a fight. At a time when you'd expect him to buckle down and grit out a way to win, he threw in the towel. That's the bottom line as far as the stoppage goes and it's something I keep in mind about him, but at the same time the guy's been in the best, beat many of the best, and it would be idiotic to hang it over his head as if it defines his career when in fact it's just one chapter.
Quitting is a big no-no in my book but that isolated incident doesn't play a big role in my assessment of Duran's legacy. Also, had he not already beaten Leonard the incident would be a much bigger deal.