I live in an area (Okanagan valley, BC) where we have a ton of fruit orchards and vinyards to pick from. I asked the bark question a long time ago as I remember reading something along the lines of bark creating more soot etc but couldn't find anything to support it. Perhaps I was thinking about using green wood and how it wasn't recommended due to 20-40% water content and other "volitiles" required to be burned off before the temperature can rise.
Either way, I don't remove the bark unless I'm using some old knarly stump stock with a real thick layer of bark.