This is part of the mystery, Clem. Is Ink turned? We hear the characters say so, but his eyes are still clear. So, if he is turned, he is still different from the vast majority of the ones we have seen. The protection aspect is not protection from the disease, as much as it is protection from the biters, themselves.

What we know is that he has clear eyes.
One of the marks seems to be "do not go there" or stop or protection.