Board Thread:Theories and Speculation/@comment-26636534-20150710195521/@comment-734582-20150711174038

Chaosattractor wrote: His Susanoo's back is still wide open. It doesn't have a Yata Mirror on it. Ergo, it can be pierced by anything that would pierce any other Susanoo we've seen, and he can still be pulled out of it. Correction: he can protect Susanoo's back himself if needed. He can use shadowclones too: sharingan can copy any technique and he's seen it often enough. He could literally use shadowclones to put people into Tsukuyomi.

EDIT: For any counter-strategy you can think up a counter-counter strategy. But itachi never showed his Sword and Mirror until he fought Sasuke and later Nagato. It would not just require extensive knowledge, but also for someone to survive against Itachi in the first place to develop said counter. Not saying it's impossible, but Nagato was defeated because his Six paths of pain was figured out in time. However, until that point he'd been uncontested because every ninja he fought made the same inevitable mistake. Knowledge is half the battle.