“none of the major communies have that hint in their description”
because the “[OC]” convention predates Lemmy by a LONG shot (easily predates Reddit as well)
“I have not seen [OC] on any post in /memes”
any of the c/memes communities are not going to be focusing (or care) about original content – and since most memes are closer to the Ship of Theseus (or more accurately, layered palimpsests), it’s hard to call it OC – the current poster would be closer to a conductor or a DJ than to a creator …