In the most recent edition of HSDS, Jin Yong edited out the scene of Sung Ching Sheu's execution by his grandteacher, Cheung 3 Fung. Jin Yong never stated his reason for making this change, but I think it's likely because he didn't want Cheung 3 Fung to appear cruel.
I'm not sure I see Cheung 3 Fung's execution of Sung Ching Sheu, as depicted in the first two editions of HSDS, as cruel. If anything, it seemed to be a mercy killing. Through his own mistakes, Sung Ching Sheu had ruined his life, leaving him a quadriplegic vegetable, a disgraced traitor to his sect, and a murderer of his own seventh martial uncle, to say nothing of being exploited and played for a fool by the woman he loved. When Cheung 3 Fung landed that lethal strike upon Sung Ching Sheu, it seemed more an act of compassion than an act of punishment.