I'm transcribing the WoT questions from that same signing in Orem, from a recording made at the signing table. And while I think Brandon's previous comments had already made this clear, this should put to rest the arguments that they did not:

Question: Okay, great. Second question. Does Demandred even have an alter ego?
Brandon: Yes, he does.
Question: Okay, cause we've been trying to figure out who the heck is it, and we can't figure it out. We're thinking Roedran, but it's like, too obvious.
Brandon: Here's the thing: Robert Jordan said that Demandred did not appear until Knife of Dreams, and so I have been very hesitant about saying whether or not he'd appeared—I think I've said whether or not he'd appeared on screen in my books—but the reason is, if I give you a yes or no—if he's appeared, yes or no—then that narrows it down to like just a few characters, that are introduced [in mine?], so I've been very hesitant about answering that. Demandred does have an alter ego. He has been up to some very cool things. There are people online who have guessed correctly. And so, I will say that much.
Question: Is he in Randland?
Brandon: I won't say whether or not he's in Randland.
Fan: He's not in Shara! He can't be in Shara!
Fan: Okay, next question.

Edited to add link to full transcript of WoT questions from Orem.