"Here comes", I posted pretty reasonable positions in the last thread and was watching this game, but thanks for your input. Being a fan of Hischier doesn't mean I dislike or hate Pettersson as you seem to think, and it definitely doesn't impact my objectivity to a hit.
It's difficult to tell from any of the angles whether the side of his head actually slams into the ice, because he landed on his side and the net is obstructing the view a bit. It may have, but it's not required to give him a concussion, you can get one just from the whiplash of his head quickly moving and stopping. Either way, that isn't the point, his head wasn't "slammed into the ice" by Matheson as people keep claiming, he was thrown into the ice by him and it resulted in a head injury.