I think the Kessel essay leans a little too much on what he sees at the "intention-based morality". He cites it over and over again but provides only a small amount of evidence to back that up as the main thrust of the book.
Throughout Ender’s Game, we are urged many times to judge a character’s actions not on their effect (even when that effect is fatal) but on the motives of the person performing the action.
But he only really offers a couple of points to back up this very, very large claim that this is practically the entire theme of the book.
Ender is portrayed as good, but not really good. I think Valentine is the only one that I can point to as truly good; and that's mainly because she is presented as a side of Ender.
Ender is ruthless when he is moved to conflict (normally by being pinned into a psychological corner of some sort) - overly ruthless. The adults purposely keep the results of his battles from him - the same way they would do with the simulator - in order to keep this ruthlessness of purpose. If he was actually to see the repercussions of his actions, he would probably cease to be quite so ruthless, because unlike Peter (as portrayed in Ender's Game only..ignoring the other books), he has a heart (like Valentine).
There's a good and evil thing going on here - Peter portrayed as Ender's dark side, and Valentine as his good side. It's pretty clear that the adults want a mix of both. The good side that lets you be a good leader, and the dark side that they need for the ruthless sort of war they feel they need, after two devastating invasions.
I think Kessel over argues Ender as a hero, and inadequately backs up his premise that Card is presenting an intention-only based morality.
For some reason this discussion makes me think of the documentary "The Fog of War" in which Robert McNamara, amongst many other things, discusses the devastating firebombing of Japan during WWII. Moral or immoral? Things aren't quite so simple. In war, one is both a hero and an immoral killer. I think that's the same kind of theme Ender's Game is striving for.