If you shoot a selfbow and use your knuckle for an arrow rest, that's when the old rule of thumb comes into play. Right wing feathers take the leading tip of the bottom hen feather right into the knuckle of a right handed shooter and, if you don't have that feather tacked down and covered with glue pretty well, you can get all kinds of cut up. Left wing feathers take the leading edge of the feather into the bow instead of into the knuckle.

If you shoot off the shelf or use a rest, 'it don't matta'.