I’ve been modifying the formatting.php file to change how WP reformats text in pages and posts.

As of WP 3.3, the edits need to be made at lines 56 and 57. The static characters are the same but the replacement strings are longer.
The array elements are highlighted red below.

$static_characters = array_merge( array(‘—‘, ‘ — ‘, ‘–‘, ‘ – ‘, ‘xn–’, ‘…’, ‘“’, ‘\’\”, ‘ ™’), $cockney );
$static_replacements = array_merge( array($em_dash, ‘ ‘ . $em_dash . ‘ ‘, $en_dash, ‘ ‘ . $en_dash . ‘ ‘, ‘xn--‘, ‘…’, $opening_quote, $closing_quote, ‘ ™’), $cockneyreplace );