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Go through this link will give you a nice work around 

https://www.drupal.org/node/170065 

Then, you need to change code: Find your modules/comment/comment.module file, open it in a text-editor (like wordpad or the like), and search for the text you don't want to see on pages. You need to comment out (or delete) a bit of code, something like:
//   

 if (variable_get('user_register', 1)) {
//      return t('&lt;a href="@login"&gt;Login&lt;/a&gt; or &lt;a href="@register"&gt;register&lt;/a&gt; to post comments', array('@login' =&gt; url('user/login', $destination), '@register' =&gt; url('user/register', $destination)));
//    }
//    else {
//      return t('&lt;a href="@login"&gt;Login&lt;/a&gt; to post comments', array('@login' =&gt; url('user/login', $destination)));
//    }
    return '';


The added 'return' is just for case, to ensure nothing to show - I didn't test this.

You can either edit the original file (which is quick but unclean, and requires you to redo the change after every unpgrade), or override that function in your theme properly by placing its copy into your template.php file (whole function!), renaming it to "phptemplate_[name]", and changing as needed. I think (not tested!) that it should look like this (added to 'template.php' in your theme's folder / create the file if not existing yet, with 

function phptemplate_comment_post_forbidden($nid) {
  global $user;
  if ($user-&gt;uid) {
    return t("you can't post comments");
  }
  else {
    // we cannot use drupal_get_destination() because these links sometimes appear on /node and taxo listing pages
    if (variable_get('comment_form_location', COMMENT_FORM_SEPARATE_PAGE) == COMMENT_FORM_SEPARATE_PAGE) {
      $destination = "destination=". drupal_urlencode("comment/reply/$nid#comment_form");
    }
    else {
      $destination = "destination=". drupal_urlencode("node/$nid#comment_form");
    }

//    if (variable_get('user_register', 1)) {
//      return t('&lt;a href="@login"&gt;Login&lt;/a&gt; or &lt;a href="@register"&gt;register&lt;/a&gt; to post comments', array('@login' =&gt; url('user/login', $destination), '@register' =&gt; url('user/register', $destination)));
//    }
//    else {
//      return t('&lt;a href="@login"&gt;Login&lt;/a&gt; to post comments', array('@login' =&gt; url('user/login', $destination)));
//    }
    return '';

  }
}


But still, you'll probably need to check on every upgrade, whether this copied code is in sync with core's possible new changes.