[El_Muerte]

You might also want to add the following plugin

global $vbulletin;
$mepattern = '/(^|\s)\/me([^\r\n]+)/is';
if(preg_match($mepattern, $previewmessage))
{
    $previewmessage = preg_replace($mepattern, '$1<b>* ' . $vbulletin->userinfo['username'] . '$2</b>', $previewmessage);
}

under the hook: newpost_preview

and

$mepattern = '/(^|\s)\/me([^\r\n]+)/is';
if(preg_match($mepattern, $reviewmessage))
{
	$reviewmessage = preg_replace($mepattern, '$1<b>* ' . $username . '$2</b>', $reviewmessage);
}

under the hook: newreply_form_reviewbit

with this the preview of a post will also get the right update

or simply download the attached xml file (note: I made it a product because of the 3 linked hooks)