Reading through the posts in that thread on GPDO so far, apparently there's a Mississippi court ruling that being in a holster is considered "concealed in whole or in part", so requires a permit.
(They recognize a GA permit, so the person arrested should be good to go.)
But that got me to thinking... Is there such a thing as clear Kydex?
(I'd buy one.)
Or could plexiglass be shaped into a workable holster?
Worst case, how about several layers of heavy vinyl?
If not being able to see all the pistol = concealment, then someone needs to come up with a clear holster so people in backward states that that can carry openly w/ no permit until the laws catch up with common sense.