I believe the spider once invited the fly into her parlour, or was it her parlor? The answer probably depends on whether you're English or American. But the question is, which spelling would you expect in a novel, and what difference would it make. When a Regency heroine invites the "Honourable Fred" into her "parlour," English readers accept the words (and spellings) without a second thought, while American ones, those attuned to Jane Austen movies at least, hear and smile at a peculiarly English tone of voice. Meanwhile, when the Regency heroine says "parlor" (or "honor"), English readers hear an American voice, quickly setting the scene as somewhere across the Pond... but what do Americans hear? (Or Australians even?) If it matters that your readers hear an English intonation, it might be good to use English spelling, in dialog at least. But that gives rise to the vexing question of what spelling to use in narration. Is the narrato...