We don't really "know" anything about his role. What he has told us may be true, mostly true, or completely false. I still find it hard to believe that the game started with two different third party factions.
I believe he may be a Doctor of one scum variety or another, and may have doctored his PM to some extent.I believe Demon posted his real role PM and that he is not scum.
Are you saying Demon has been a noisy player?I think we are being biased towards noisy players and letting the quiet ones slip through. All of this madness is making town jump. But I still believe the simplest explanation is that scum don't want to make waves.