paul, the Boychuk play was VERY different than the Chara-Pacioretty incident. The way I see it, they both were skating towards the corner when the puck was headed there. Then the puck made it's way into the middle of the ice, and their momentum carried them into the boards. Raymond going in "butt" first if you will was probably what caused the injury. He hit the boards and his spine got crunched. Boychuk didn't send him flying into the boards and didn't exactly guide his head anywhere specific like Chara did.
In my opinion, that's why the NHL didn't see the hit as malicious and regarded the injury as an unfortunate accident that occured because of Raymond's body position and both players momentum. Boychuk did not necessarily cause the injury. That being said, an interference penalty would probably have been warranted, but no more than that I don't think.