Board Thread:Theories and Speculation/@comment-26388300-20150612203442/@comment-3568954-20150618120102

Thekillman

you are assuming that Kabuto knew that the contract could be undone by the soul that is summoned being that he believed it was a perfect jutsu with no flaws he likely didn't know about that flaw as he himself said that Edo tensei is a perfect jutsu with no weaknesses on multiple occasions, so one must assume that he did not know about it.

one must also assume that had kabuto attempted to take control with the paper tag that Madara would release himself before he could do it(this is madara so obviously he is way to OP)

another thing madara had no reason to release the contract because Kabuto was working on the same side, sure he most likely knew that Kabuto believed he was in control but madara being a genius was likely not releasing himself as a tool(if needed he could simply get information out of kabuto) there was no tactical advantage of releasing himself from the contract not until itachi had kabuto undo the jutsu

another option would be that madara may have had a way of destroying the paper tag in him so it might not have been possible to overright his mind with the paper tag