>>720137458
The case for a doorway is different because in a regular, non-portal doorway, both side of the doorway move at the same speed. See: >>720135046
>With B, you are creating energy with more energy coming out than went in.
Yes, portals would violate energy conservation. You don't need to move portals for this. Just make a portal between the floor and a ceiling of a room, stick a turbine in there, and then pour in water. There you go, infinite energy (turbine wear notwithstanding).