Get Drupal 7 comment forms to display error messages on the original node's page

yourmodule.module

function yourmodule_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'comment_node_blog_post_form') {
    $form['actions']['submit']['#value'] = 'Add Your Comment';	
    $form['#action'] = '?'. drupal_get_destination(); 
  }    
}