Note that the McWhorter articles are over two years old. He is specifically talking about the comma, and again only in short messages, like texts and tweets. He is not talking about punctuation in general or in other forms of writing. The Slate article, linked in the Daily Mail piece, is a much better discussion of McWhorter’s point. The Mail conflates McWhorter’s discussion with the disappearance of apostrophes from UK road signs, something that was happening two years ago.