England and Wales: British politeness is a code
Then there is the layer underneath: "not bad" meaning good, "interesting" meaning no, "we should do that sometime" meaning we will not. None of it is dishonesty. It is a shared agreement to lower the volume.
Wales changed the tone again. I learned one word, "diolch", and used it in a shop, and the whole conversation warmed by several degrees. One word.
That is the lesson I keep taking to lessons: fluency is not vocabulary. It is knowing what a sentence is doing, not just what it says.
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