It is a matter of an opinion. In my opinion, it simply does not fit his character. As I pointed out in that discussion, Vader never looses his temper before, even when he has obvious reasons to be pissed off. Instead he reacts calmly and simply executes people (many times he accompanies it with witty remarks). That’s all I am going to say.

Edit: Sorry, I couldn’t help myself, but maybe they should change the scene when Luke jumps. Instead of Vader calmly dropping his arm, they should add “NOOOOOO!” to signify his anger…