I see shorts of various lengths on the streets all the time. I figure that a kilt can be of whatever length the person wearing it wishes. I prefer at the top of the knee for comfort and so that it doesn't hit the back of the knees; but that's just my take.
Past President, St. Andrew's Society of the Inland Northwest
Member, Royal Scottish Country Dance Society
Founding Member, Celtic Music Spokane
Member, Royal Photographic Society