WordPress beautifies single and double quotes, which can be a pain, when someone is posting a code sample. Going to functions-formatting.php inside wp-includes folder and commenting the lines below out removes all beautification for quotes:
$curl = preg_replace("/'s/", '’s', $curl);
$curl = preg_replace("/'(\d\d(?:’|')?s)/", "’$1", $curl);
$curl = preg_replace('/(\s|\A|")\'/', '$1‘', $curl);
$curl = preg_replace('/(\d+)"/', '$1″', $curl);
$curl = preg_replace("/(\d+)'/", '$1′', $curl);
$curl = preg_replace("/(\S)'([^'\s])/", "$1’$2", $curl);
$curl = preg_replace('/(\s|\A)"(?!\s)/', '$1“$2', $curl);
$curl = preg_replace('/"(\s|\S|\Z)/', '”$1', $curl);
$curl = preg_replace("/'([\s.]|\Z)/", '’$1', $curl);
$curl = preg_replace("/ \(tm\)/i", ' ™', $curl);
$curl = str_replace("''", '”', $curl);

Thanks! Before your fix, those bloody quotes have been causing problems in my feed for months. Cheers!
Thanks. I’m trying to use Wordpress to display ActionScript code.
Can’t thank you enough. Googled for a couple of hours trying to get around one apostrophe in one important post.
This fix was the bomb
Dan
Any chance there’s a fix for this that is WP2.x compatible? A plugin would be nice, but I’d take anything…
Nice work – been looking for a solution to this.