selectively-disable-disqus.php

<?php

/*
Plugin Name: Selectively Disable Disqus
*/

add_filter( 'the_content' , 'mh_disable_disqus' );
function mh_disable_disqus( $content ) {
        $id = get_the_ID();
        if( $id == 123 ) {
                remove_filter('comments_template', 'dsq_comments_template');
        }
        return $content;
}