Hmmm well I think if they shoot fire arrows/bolts there is always the possibility to vegetations/ground burn, even if they want it or not. If they dont want to start a fire in the forest they shouldnt have this skill. Hehe its pretty weird for me that orc's and human's fire burn and the elven's fire dont, fire is fire for me hehe. But anyway I see your point.
Thx for the answer and good job for the game. Ill be waiting for the xpack ^^