User blog comment:Madman97/You know what really grinds my Wabbajack's? S3E1: I can't kill these guys/@comment-25109952-20131025182427/@comment-11345660-20131027175731

Or maybe at a certain point in the quest, the person becomes killable, rather than after the quest is completed. Thus, you could do the quest in two ways. One way if they're alive, one wayif their dead. Thus, the quest would still be able to be completed, while adding diversity to the game.