I don't think Jefferson is a mafia member. If you hadn't caught his post, you could obviously tell what it was by the mods reply. They then announced that his role was changed. His role was a pro town, I doubt they'd give him a new role that was pro mafia. It gives the mafia an unfair advantages, which wouldn't have been good since it's the beginning of the game and nothing has unfolded quite yet.

That being said, I don't think he's Innocent. I just think he's not a suspect at the moment. But this seems like common sense to me.