What is needed for pingbacks to show as comments?

<link rel="pingback" href="<?php bloginfo('pingback_url'); ?>" />

is in my header.php

but pingbacks are only showing up in the admin. I approve them, and my comment list on the blog post will say “1 reply,” for example, but the pingback doesn’t show as a comment. I’ve been comparing the comments.php from different themes but can’t see anything that would specifically call it. I have found this commented out on most of them:

<!--
				<?php trackback_rdf(); ?>
				-->

but it is my understanding trackbacks are different and that is not needed for pingbacks.

What else can I look for to discover why pingbacks aren’t displaying?

Plugins I’m running are:

Akismet
Clean Archives Reloaded
Maintenance Mode
Run PHP

None of which should interfere.