Most of the major heroes in Jin Yong's novels became legendary figures to future generations. In LOCH, such DGSD titans as Kiu Fung, Hui Juk, and Deun Yu were spoken of reverently. Similarly, in HSDS, Gwok Jing and Yeung Gor were remembered as the greatest heroes of their time. In DOMD, Ling Wu Chung was regarded as a prominent wulin figure of his era.
But there were never any references back to Cheung Mo Gei in novels that post-dated HSDS in continuity, despite the high level of martial arts he achieved and his many heroic accomplishments in the wulin of his era.
Is it possible that Cheung Mo Gei's heroic legacy was sullied by Chu Yeun Cheung as part of the latter's process of ascending to the position of founding Ming Emperor? Remember: to reach the position of Emperor, Chu first had to set Cheung Mo Gei up to quit as leader of the Ming Cult. Then, Chu Yeun Cheung had to bide his time until Cheung Mo Gei's successor, Yeung Siu, was too old to continue to effectively lead the cult. At that point, Chu Yeun Cheung took over as Cult Leader and, after the Mongols were repulsed and the Ming Dynasty took hold, wiped out the cult. To justify his actions to his followers, Chu Yeun Cheung could not let the Ming Cult look good; they had to be identified as traitors and enemies (much like what Darth Sidious/Emperor Palpatine did to the Jedi Order in STAR WARS: REVENGE OF THE SITH). Hence, it wouldn't do for Cheung Mo Gei to maintain this heroic reputation. I think Chu Yeun Cheung rewrote wulin history and somehow diminished Cheung Mo Gei's legacy.