Calzaghe was ahead of the cards and the cut was caused by a punch, so the result wouldnt have changed whoever was cut. Ive seen lesser cuts stop a fight though, that was a horrible gash. If it wasnt RJJ last throw of the dice i think they wouldve stopped it.
No but one of the British commentators, I think it was Richie Woodhall, said that if that had happened in England the fight would've been stopped without a doubt.