Stop indexing drupal reply comment pages

If google indexes every content node twice, one time the goog one and additionally the comment creation url, just enter this into your themes template.php

function YOURTHEME_preprocess_html(&$vars) {
...
  if(false !== strpos(current_path(), 'comment/reply')) {
    $myelement = array(
      '#tag' => 'meta',
      '#attributes' => array(
        'name' => 'robots',
        'content' => 'noindex,noarchive',
      ),
    );
    drupal_add_html_head($myelement, 'robots');
  } // if
...
} // function

Change the function name to your theme name or just add the if block into an existing preprocess function.