In reply to Italics & Punctuation:
Perhaps, and I don't entirely abide by it, but as a rule it does look very handsome.
What he's really doing is treating brackets and parens like math signs are usually treated — as geometrical symbols, and not letters. Whether you italicize them (or design italic symbols, if you're a type designer) is an expression of your opinion on the matter: are they quasi-alphabetic characters, or are they signs that exist separate from the different styles of type that letters embody?