The problem is when I jump over some object and suddenly see the enemy. You say I should stay defenceless for a while?
No as you are jumping over the wall/object and not simply behind it, you have already committed to the obstacle and not stayed behind it.The enemy in this case has a clearer shot and your advantage of the wall/object is diminished as you are now more exposed.
Jumping over obstacles is part of game play and if an enemy appears then fine shoot. But sitting behind and shooting and jumping is in my books a no no. Although some players recently appear to use this tactic to their advantage and jump over an obstacle and fire and shoot. We cannot police every move but take a sensible approach to the rules.