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Ah I see. I was thinking of motte and bailey as something like a fallacy or a singular argument tactic, not a description of a general behavior. The name makes much more sense now. Thank you. Also, you said it's called that "everywhere except the Scottosphere". Could you elaborate on that?
Scott introduced the concept of a motte and bailey doctrine on Slate Star Codex, in an article called Social Justice and Words Words Words or something like that. I don't think he said anything that was wrong in that post (about that concept), but it appears that a lot of readers who hadn't heard about M&BDs before misunderstood it to be about a debate tactic/fallacy. So on SSC and to some extent on LW 'motte and bailey' is often used with the meaning 'bait and switch'.