Convert comments to Custom Post Type

OK @John Enxada i looked in the theme admin part. The thing which you are asking is difficult but possible. The first thing you have to check that how they are creating relation between two post types i.e relation between thread and replies. I have no excess to the database(can’t see in database to check how they relate). You have to do it by yourself.

For this you have to create a script yourself. I can only help you how to create it. First get the backup of your database so that if anything go wrong you have a backup.

Once you know then you can change the post type of post to thread. Which you did already. Then you can get all the posts of thread using get_posts function. Then using a for/foreach loop get all the comments of each post one by one using get_comments. Again apply a for/foreach loop for each comment one by one. Then using wp_insert_post insert these comments as a post having post_type = replies.

Here is an code that will help you somehow.

$args = array(
    'posts_per_page'   => -1,
    'post_type'        => 'thread'
);

$threads = get_posts( $args ); // Get all posts of thread.
foreach($threads as $thread):
    $comment_args = array(
        'post_id' => $thread->ID
    );
    $thread_comments = get_comments($comment_args); // Get all comments of the post.
    foreach($thread_comments as $thread_comment):
        $reply_post = array(
            'post_status'  => 'publish', // Set replies status.
            'post_type'    => 'replies', // Set post type.
            'post_author'  => $thread_comment->user_id, // Set comment user id as post id.
            'post_title'   => 'RE: '.$thread->post_title, //They prefix RE: to every reply so i think we might be do the same.
            'post_content' => $thread_comment->comment_content // Set comment content as post content.
        );
        wp_insert_post($reply_post); // Insert the comment as post having post type replies.
        // Write the code through which they create relation between these post types
    endforeach;
endforeach;

These are some important value which a post must require while inserting. But i think they are inserting some more values as post_meta. So you have to look onto those values also. Once you start the script it will convert all your comments to posts having post_type = replies.