From the implementation guide on Yoasts site, it says:
<?php if ( ! empty($comments_by_type['tweetback']) ) : ?> <h3 id="pings">Tweetbacks</h3> <ol class="commentlist"> <?php wp_list_comments('type=tweetback'); ?> </ol> <?php endif; ?>
If I do not have the if around the wp_list_comments area I see a tweetback result, however when it is inside this if statement I do not. I've tried several other alternatives but cannot get a filtered state to only show when tweetbacks exist.
Closest I got was trying to write wp_list_comments into a variable and if that was empty then display, but it does not have an option to echo as a variable and the callback function was giving me fits.