Board Thread:Naruto Discussions/@comment-32104334-20171109032930/@comment-734582-20171203205815

Namikazenaruto9 wrote: Orochimaru knew the moment he used edo tensei on Hashirama that he could break and that was definitely not the case with him. Kabuto mentioned earlier that while for some he had to repress their personality, other Edo were best left with free will. When Itachi and Nagato fight they mention they have no control and eventually are not able to respond freely. But Madara was talking to Kabuto, talking to the Kage, saying stuff about his power etc. All indications were that Madara was free to act. Kabuto implies to Madara that he revived him just to confirm his theory about the Rinnegan.

Secondly, Madara undoes the Edo Contract simply by making the signs, so at any point he could've done the same. He simply chose not to.