Reasonably easy answer. In skins/skinname/_main.php I added

$feedback_id_done = false;	// workaround for xhtml validation issue

to the first 'feedback type' block, then changed it to true for the remaining 2. Then over in skins/skinname/_feedback.php I replaced

echo '<a id="feedbacks"></a>';

with

if( ! $feedback_id_done ) {
	echo '<a id="feedbacks"></a>';
	}