"That's something, at least. I know the whole relying on a computer to supplement basic brain activity isn't ideal, but clearly you haven't given up on being alive in spite of that."

Donnie's not much for knowing how to offer encouragement, much less how to be reassuring, so he always defaults to facts, and there's enough he's gleaned from observation to plug together. Pros and cons. You just ignore the obvious cons because in this case, the other party's well aware of those.