Closures break the high-performance part of things. If we could have just used JavaScript, we would have done so - KL is as close to JavaScript as we can get, and still offer native, multi-threaded performance. If we introduce inferred types, then the only difference will be 'no closures'.
That makes sense, I'm sure it is hard to optimize closures and untyped code. However, if you remove those you no longer have JavaScript so it is incorrect to say that you have made Javascript fast, you've just created a different language and made that fast. Of course if it plays nicely with Javascript that's cool, but please say that!
