Second comments section for one post/page

by

When you add/display comments you could use a different comment_type 

$data = array(
    'comment_post_ID' => 1,
    'comment_content' => 'content here',
    'comment_type' => 'comment_type_a',
);

wp_insert_comment($data);

This means you can query comments by comment_type depending on where you want to show them.