Amazon put "has flat buttocks" in writing about a real customer. And there's a page where you can read what it wrote about you, right now, in your Amazon app. The file itself is 20 years old. Amazon has always run this kind of inference. Buy padded leggings once and a model somewhere concludes things about your body. For two decades that conclusion lived as a vector, a few thousand numbers no human could read. Not you, not anyone at Amazon. The creepiness was invisible because the format was…