Board Thread:Site Discussion/@comment-32623270-20170719125809/@comment-26500386-20170719132733

Aizawa's Quirk can't erase Mutant types. That's my conclusion.

Let's use Four Arms as an example - This Quirk gives the user four arms. Thats part of their body, and they can't ever be switched off - you can't switch off having four arms, hence, Erasure wouldn't work on it. With this in mind, and considering he was unable to erase the arms of the Heteromorphic type Quirk Villain in the USJ, this further suggests that Four Arms would be unaffected by Erasure.

With chapter 135, I agree it was very poorly worded - It's now not clear as to his exact limits are with his Quirk. I'm inclinded to beleive he simply cannot effect Mutant Type Quirks because chapter 14 said so, and we've never seen him erase any effects of a mutant type Quirk throughout the manga.