Duen Yu's mother Do Bak Fung had a different surname - Shu Bak Fung.
The four evils in the old edition were part of the 7 wu-lin elders, known collectively as the 'sam sin sei gnok' (3 gentles, 4 wickeds). However, JY never actually said who the 3 gentles were, and appeared to change course halfway through the novel, such that the most reknowned fighters became 'northern Kiu Fung, southern Mo Yong' again.
Ah Bik could use her music in inner-power competitions and to free sealed pressure-points remotely. When they were held hostage by Kau Mor Chi, she used her music to discretely free Duen Yu, who seriously injured KMC in a suprise '6 mak san gim' attack that skewered his shoulder.
Ah Bik was Hong Gong Ling's student (So Sing Hor's oldest student). She had accompanied the 4 Mo Yong generals to Shaolin searching for Ah Chu, and was also captured along with the others by Ding Chun Chau. The Mo Yong family left her behind with her sifu and we don't see her again until the very end.
There are numerous changes in the names of minor characters such as the students of the Mo Leung sect, that aren't really worth mentioning.
The paralysing 'bei so ching fung' gas favoured by the Sai Ha army was originally called 'hung fa herng mo' (red flower fragrant mist).
Ah Chu and Ah Bik did not have the funny accent in the old editions.
In the old editions of Jin Yong novels in general, it has been repeatedly mentioned that the victims of 1 yeung finger do not suffer any pain (even when they are killed by it), but feel comfortable, warm and lazy.
Ding Chun Chau and Yip Yi Leung seemed to have a past history together, with YYL calling DCC 'Chun Chau gor gor' in the most 'yuk ma' fashion possible. When Hui Juk found out who his mother was, he was afraid for a moment that his father might be DCC!