Board Thread:Theories and Speculation/@comment-27924662-20161219053341/@comment-734582-20161219082421

Namikazenaruto9 wrote: That statement refers to the How infinite tsyukoyomi is cast, that power of rinne here refers to rinne-sharingan and in this case hagoromo was shown not to have it. No, the power of rinne refers to the rinnegan and it quite clearly says the Rinne Sharingan will awaken when approaching the moon.

I think there are two options: 1: As i've said in countless other threads, Hagoromo only possessed the Juubi Chakra until he nearly died and took in the Gedo. (A necessary condition to reconcile 4 or so different versions of events). Hagoromo didn't awaken Rinne Sharingan because he didn't possess the full Juubi and even when he had the Gedo Statue in him, the two halves weren't remade into one.

2: If we go by the story that he does have the full Juubi, then i'd say that the red mark on his forehead is a seal which surpresses the power of the Rinne Sharingan, to make sure that Hagoromo never goes crazy like his mom.