The logical extrapolation of your argument also says that there’s no such thing as a bug—just software that doesn’t do what you in particular, or perhaps everyo

The logical extrapolation of your argument also says that there’s no such thing as a bug—just software that doesn’t do what you in particular, or perhaps everyone, wanted and expected it to do. Also you suggest that there’s no such thing as a design mistake, yet that opinions can be categorically wrong or right. These seem to me to be mutually incompatible. At the very least, the first part necessarily restricts the type of opinions that can be categorically wrong, so that the designer of something can’t correctly declare something a mistake. One popular list of design mistakes in a language is https://eev.ee/blog/2012/04/09/php-a-fractal-of-bad-design/ https://eev.ee/blog/2012/04/09/php-a-fractal-of-bad-design/. Many of them can be quibbled over, but many of them are unequivocally at the very least suboptimal, where the behaviour that was complained of was quite indefensible—and commonly has been fixed since, because in many cases it was considered a bug. (And so you see how the line between a design mistake and a bug can be fairly arbitrary.) Another example I’d use of an unequivocally bad design is MySQL’s Unicode charsets: that you had utf8, then utf8mb3 and finally utf8mb4. utf8 and utf8mb3 were both stupidly broken from the very start, utterly unfit for purpose. They should probably never have been invented, but at the very least they should have been named differently—tens or hundreds of thousands have learned the hard way that “utf8” is dangerously broken, and that “utf8mb4” is what they need.