How To Open The Comment Form In Modal Form I want To Provide The Link "Add Reviews" For Content Type Example "Doctor". Then How I can Use the Comment Functionality For That. So that When the user Click on the Add reviews Link A modal Form  Appears  Having Text Field with "Rating Star". so that user can submit Reviews For that Content Type.
You can use Colorbox Node.

So you should have this link in your node.tpl.php:

print l(t('Review'), 'comment/reply/' . $nid . '?width=600&amp;height=600', array(
          'attributes' =&gt; array(
            'class' =&gt; array('colorbox-node')
                )));