The question of its extent is vexed, and I gather, to some, vexing. I do rather think that our fellow writers have nous enough to see and use such analogies as suggest themselves, e.g., 'X is a Muggle-born living nr Hebden Bridge, and doesn't support, say, Appleby, but rather, being a Lesbian - I did mention hebden Bridge, I think - the Harpies': that sort of thing.