Actual comments not showing, but form is?

Your format looks a bit off to me. I’d try it more like this:

<?php $fields = array(
                      'author' => '<p><label for="author"><span class="req">* </span>' . __( 'Name' ) . '</label><input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30"' . $aria_req . ' /></p>',
                      'email'  => '<p><label for="email"><span class="req">* </span>' . __( 'Email' ) . '</label><input id="email" name="email" type="text" value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30"' . $aria_req . ' /></p>',
                      'url'    => '',
                     );
      $theme_defaults = array(
                              'comment_field' => '<p class="comment-form-comment">' . '<label for="comment">' . __( '' ) . '</label>' . '<textarea id="comment" name="comment" cols="45" rows="8" aria-required="true"></textarea>' . '</p><!-- #form-section-comment .form-section -->',
                              'comment_notes_after' => '',
                              'title_reply' => 'Leave a Comment',
                              'comment_notes_before' => '',
                             );

comment_form( $comment_args ); ?>

Source: WordPress Codex