Isn't there that one message that says something about sneaking into a room and putting so-and-so down permanently? No fight ensues, but it's also not really "permanent". I could be wrong, but I'm fairly sure I saw this at least once.
The permanently refers to the severity of the wound. Stability is right I think, I know of two outcomes if you manage to reach your target,
"Silently, you sneak up on your target, and surprise [Name]. He awakes at the last second, drawing a dagger, but is barely able to slow your attack."
and
"Your target is quick and attentive, and spots you in time. You have no choice but to fight [name] one on one."
