Hide "Your name" field in comment form from everyone except admin
function YOURMODULE_form_comment_form_alter(&amp;$form, &amp;$form_state) {
  global $user;

  if ($user-&gt;uid != 1) {
    unset($form['author']['name']);
  }

}


Another way is, if your theme has a comment.tpl.php file, putting a condition to restrict authenticated and anonymous user.

&lt;?php print $author; ?&gt; 


To limit this to a particular content type, you can create a separate comment template file for that content type.