[jenz]

With bbPress v 1 RC – I had the same need and ended up putting this into the topic-tags.php template – and it worked great:

<div id="topic-tags">

<?php if ( bb_get_topic_tags() ) : ?>

<?php foreach ( $tags as $tag ) : ?>

<?php if ($tag == end($tags)) >

<a href="<?php tag_link(); ?>" rel="tag"><?php tag_name(); ?></a> <?php tag_remove_link(); ?>

<?php else >

<a href="<?php tag_link(); ?>" rel="tag"><?php tag_name(); ?></a><?php tag_remove_link(); ?>,

<?php endif;?>

<?php endforeach; ?>

<?php else : ?>

<p><?php printf(__('No <a href="%s">tags</a> yet.'), bb_get_tag_page_link() ); ?></p>

<?php endif; ?>

<?php tag_form(); ?>

</div>

This added the commas appropriately.