If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
If continuing the discussion becomes impractical, that means you win at open threads; a celebratory top-level post on the topic is traditional.
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Then we're all doomed.
You might be reading SarahC as saying that teaching a competent adult to change his or her habits of thought is not possible (if you're not, ignore this comment), but I think she's saying that it's not worthwhile.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
If continuing the discussion becomes impractical, that means you win at open threads; a celebratory top-level post on the topic is traditional.