I wish. It is nearly useless (in my opinion) to get an incapacitated result on a Mage, and generally would rather have other effects on my opponent. I don't remember what the spell was that I used, but I scored an incapacitated on my opponent the other day and we decided that we had to take the result that was rolled instead of the "lesser" result.
My way of looking at it is that there are a few different things that can happen depending on what out-of-game event happens related to the spell. In this case, one thing isn't a compounding of the first (except, for example, in cases like the Burn / Two Burn effects).
All this having been said, I'm just guessing and letting you know the way we read it when we played. I'm looking forward to a more informed person's answer.