I'll post what I posted on the main boards here:
This play certainly fits the mold of interference, but it is definitely not boarding. There was also no intent, nor was it vicious, and I would argue it wasn't even reckless by Smith. It should have been 2 minutes at most, and if Borowiecki had handled himself properly going for that puck battle then this unfortunate accident doesn't even happen at all.
Borowiecki went in for a battle where he had to good footing at all. The contact happened while both players were still well inside the faceoff circle and the damage was done when he hit the back of his head on the boards beyond the goal line due to his own reckless momentum, poor footing, and willingness to engage.
Hit in faceoff circle:
Borowiecki looking right at Smith and leaning in to hit him as well to fight for the puck:
Borowiecki's completely off-balance footing prior to the hit:
Furthermore, the interference rule specifically mentions hitting a player "with no effort to play the puck." Two players skating into the corner going shoulder to shoulder happens multiple times every single game - and there certainly is not "no effort to play the puck" when the players will be on top of the puck within literally a split second.
Also, I saw one poster talk about how the refs may or are allowed to increase the penalty to the 5 minute major when there is an injury. That is for nearly every single penalty. It is a subjective decision made by the referee. "May" and "allow for" are permissive, and not mandatory - it is a huge difference.