> His argument against Hindley-Milner seems to be that "he hates it", and that type errors are sometimes hard to understand. It is true IMO that they are hard to understand (even though, like everything in programming, you get better with practice), but what is the alternative? Debugging runtime errors while on production?

He pointed out that a more nominal type system is a solution. Because when you give meaningful names to your types the error messages will become clearer and not full of long, inferred types that reveal potentially confusing or unimportant implementation details.