Thank you for speaking up. Knowledgeable boxing fans are well aware of how important having a good chin is to success in boxing. Deniers DKSAB.
Even in Amir's case I feel the glass jaw factor is given too much weight. While he clearly hasn't got a reliable chin, his defensive lapses and tendency to trade when caught are more obvious weaknesses.
Fantastic thread by a wonderful poster. Yes, Glass Jaws do exist in boxing. Some fighters can take a shot, some can't. It's not some black magic or voodoo, it happens right before our very eyes.