But Korby wasn't really alive to begin with: "Doctor Korby was never here." That turned out to be the whole point.
How much of that is true, and how much just Chapel's racist revulsion at the concept of Korby having replaced his body with machinery? Certainly Korby was "there" to a significant degree, passing the Turing test with flying colors, demonstrating the full factual knowledge of the man, and behaving like one would expect from a man like that if one didn't know him intimately. And Chapel knowing him intimately might make her eminently unqualified to utter insults like that. (Okay, it's Kirk's rephrasing of something Chapel said earlier on, but still.)