According to Mediapart, the author Michel Taubmann, who wrote a political biography of DSK, was persuaded to leave out the Banon allegations by Ramzi Khiroun, DSK's PR flack and fixer, who told him DSK's version. Banon, Khiroun alleged, was angry that DSK had intervened with her editor to have the chapter about him removed from her book "because it was written in a grotesque style." She promised Khiroun that she would avenge herself for this slight, and some time later she told her story to Thierry Ardisson.
Unfortunately for DSK, Banon's editor denies that this ever happened. It also strikes me as rather "grotesque," to borrow an adjective, that an important political figure would employ a fixer to police stories written about him or that an editor would allow the subject of a profile to spike a story on stylistic grounds.