Mafia 103. Ice and Ash

but there's nothing against the Shaman, except for psychology, which I would have used if the day had ended a couple of hours ago.

That's exactly the main factor – there's nothing against him.
Many have positive points, but he has nothing.
You forget that I've played with him in many games. Including those where more is calculated based on rhetoric than on Night Detective (ND).
Moreover, I know that I can't be wrong about him, and he knows it too. In short, I wouldn't use the Commissioner to check the Shaman because I already know his status. Just as I wouldn't check Alisha, Safa, or Emilia (these nicknames probably don't mean anything to you, but they probably do to the Shaman). I don't need ND to say whether the Shaman is a villager or a Mafia member; I just need to look at him for a while. Do you understand?