This is awesome. I have two comments

1. Does this mean we don't need static type-checking?

2. Instead of

    (lambda (x y)
        (let ((xs (* x x))
            (ys (* y y)))
        (sqrt (+ xs ys))))

why don't they (the article) format it like:

    (lambda (x y)
        (let (  (xs (* x x))
                (ys (* y y))
             )
        (sqrt (+ xs ys))
        )
    )

The rule could be: Never have more than TWO consecutive closing ')' on the same line.

If you're trying to prove the benefits of a syntax, the reader should not need to spend energy on trying to understand which closing ')' correspond to which opening '('.