It shouldn't but it it is a bug with the SMF code in the sendpm function
Mainly the line $user_info['name'] = $from['name'];
function sendpm($recipients, $subject, $message, $store_outbox = false, $from = null)
{
global $db_prefix, $ID_MEMBER, $scripturl, $txt, $user_info, $language, $func, $modSettings;
// Initialize log array.
$log = array(
'failed' => array(),
'sent' => array()
);
if ($from === null)
$from = array(
'id' => $ID_MEMBER,
'name' => $user_info['name'],
'username' => $user_info['username']
);
// Probably not needed. /me something should be of the typer.
else
$user_info['name'] = $from['name'];