First off, my long list of suspicions that I linked you too wasn't exactly looking for an answer from each person, but rather to start discussion amongst the town as a whole. Everyone should have taken the opportunity to defend themselves or heap on more accusations. Technically you still have time, but you better get digging for dirt quickly.
I really don't know why zexen thinks scifi is a townie, as I really don't buy it, but I'm not confident he is mafia either.
Finally, the "you don't have evidence" argument doesn't really work. No one has posted "I am mafia" so the best we can get is speculations. Preferably speculations with some form of rational reasoning, like the "doctor" theory. The doctor theory actually makes sense, which is why I posed it. Obviously the move has been used enough that it deserved its own wiki page. However, due to the low probabilities the fact that it was right for 2 people makes me wonder if it could go 3-for-3.