[HOW-TO] Drupal 6 : Add additional "Add Comment" link into the node
<?php print l(t('Add Comment'), 'comment/reply/' . $node->nid, array('fragment' => 'comment-form')); ?>
Make sure that , 'comment/reply/' part is relative to your path. If you access your website through www.myweb.com/web. Then, that part would be , 'web/comment/reply/'