I achieved this by adding echo '<span>'.(($Discussion->CountComments) - 1).'</span>';
after this line echo '<li><a href="'.vf_combine_paths(array($link_url, 'discussion/'.$Discussion->DiscussionID.'/'.vf_format_url($Discussion->Name)), '/').'">'.$Discussion->Name.'</a></li>';
echo '<span>'.(($Discussion->CountComments) - 1).'</span>'; in widgets.php wp-content/plugins/vanilla-forum/
Answers
echo '<span>'.(($Discussion->CountComments) - 1).'</span>';
after this line
echo '<li><a href="'.vf_combine_paths(array($link_url, 'discussion/'.$Discussion->DiscussionID.'/'.vf_format_url($Discussion->Name)), '/').'">'.$Discussion->Name.'</a></li>'; echo '<span>'.(($Discussion->CountComments) - 1).'</span>';
in widgets.php
wp-content/plugins/vanilla-forum/