This is Gfy... there are verying degrees on the definition of professionalism here. Additionally, there are plenty of folks who don't act consistently on/off the board - you may meet Mary Poppins off the boards, but Medusa on the board.
You know how you've heard girls bitching because their boyfriend doesn't treat her the same privately as he does around his friends? Think of it as something like that.
Me personally, I act the same no matter where I am - it's less work and leaves less open to interpretation.
*edit: can't type.