Sorry to double-post, but I've only just realized that I'd like to go to bed and then sleep really late tomorrow, as it's my only day off from classes and I need the rest.
That means that I'm voting now for
++Mister Underhill
Before, his quiet "playing dumb" nature bothered me because we all know that he isn't dumb. Then I started rereading the thread and realized just how many people suspected him. Then I realized that I suspected him, and that was quite the shock to learn. Here I'd been vaguely concentrating on B88 and LMP. I guess that's what I get, being distracted by Rëâl Lìfè and all of its complications.
Not saying B's innocent, mind, just that I currently think Mister Underhill is the bigger problem to be solved tonight.