Taking Control

When you use cards such as Turn Against the enter the battlefield abilities trigger when the creature returns to the opponents control, but not when you gain control. Surely this should be neither (since it's not actually entering the battlefield) or on both switches of control, not just in favour of the opponent.

Similarly in situations when you gain control of something like Hangarback Walker and it's destroyed, the destroy ability triggers in favour of the opponent and not the current controller of the creature.