I noticed in IE6 there is a JS error because of an dangling comma at the end of the MCE init params object.
Here is a fix at line 247 of TinyMCEComments.php which had this:
foreach ( $initArray as $k => $v )
$res .= $k . ':"' . $v . '", ';
I changed it to this so that there is no ending , in JavaScript for IE to choke on.
$params = array();
foreach ( $initArray as $k => $v ):
$params[] = $k . ':"' . $v . '" ';
endforeach;
$res = join(',', $params);