I don't want to divert your discussion of the Fort Blakely capture, but I would be interested in seeing a discussion of the historical pedigree of this "red field, white crescent and white Palmetto" variant of the South Carolina flag tradition.
See Glenn Dedmondt, "The Flags of Civil War South Carolina" (Pelican Publishing, 2000).
Glenn left out the Citadel flag - red field, white crescent and white Palmetto. It would appear that you have found one. I believe this variant has been adopted, perhaps informally, by students of The Citadel, The Military College of South Carolina. I certainly see a lot of them displayed in public when I visit South Carolina each year.