Including comments meta box on a plugin page

You can also use add_meta_box to add predefined boxes to different places in the admin, as long as you know the right handles. In the case of the comments meta box you need:

add_meta_box('commentsdiv', __('Comments'), 'post_comment_meta_box', $screen, 'normal');

Here post_comments_meta_box is the callback function that fills the metabox. I am supposing your plugin is setting a current post, because the callback needs it (it doesn’t make sense to display a comments meta box if you don’t specify which post the comments must be taken from). $screen is the location of your plugin admin page.