Board Thread:Versus Debates/@comment-29899821-20160317090255/@comment-734582-20160402162736

Ravenlot 27 wrote: Not completely uncannon. It's non-canon. Though it's obviously also uncannon.

As to levels of canon, i thought it was established that Manga trumps all. Since not even Danzo was aware of what Susanoo looked like (he does say "so this is susanoo?" when facing Sasuke) and Danzo would've been aware of Shisui's Susanoo, it's clear that Shisui never got to that point. Why is not clear, but Sasuke's awakening of it shows that it's not exactly a pleasant ability, use of the Mangekyou makes it deteriorate faster and shisui's style of battle would make bad eyesight even more inconvenient than for people like Itachi.