> I speak of the elegant, elongated hyphen, the gentle friend and ally of all writers, used to set off a chunk of text within a sentence.

There's nothing elegant about a punctuation mark firmly glued to the words on either side, making a sequoia-sized typographic log that typically gets wrapped in its entirety to the next line, leaving a half mile or so of white space just hanging in space before the wrap.

If you're gonna use the em dash, make sure your software can break a line on either side of one.