add_action('comment_post','wp_000_reg_user',10,2);
function wp_000_reg_user($comment_ID, $comment_approved) {
    if( 1 === $comment_approved ){
    $userdata = array(
    'user_login' =>  sanitize_user($_POST['username']),
    'user_email'   =>  sanitize_email($_POST['useremail']),
    'user_pass'  =>  sanitize_email($_POST['userpass']),
    'role'  => 'subscriber',
    'show_admin_bar_front'  => false
                );

    $user_id = wp_insert_user( $userdata ) ;

    // On success.
    if ( ! is_wp_error( $user_id ) ) {
       wp_redirect( get_permalink() ); exit;
    }

       } //end if
    } //end function

if ( !function_exists('wp_new_user_notification') ) {
    function wp_new_user_notification( $user_id, $plaintext_pass = '' ) {
        $user = new WP_User($user_id);

        $user_login = stripslashes($user->user_login);
        $user_email = stripslashes($user->user_email);

        $message  = sprintf(__('New user registration on %s:'), get_option('blogname')) . "rnrn";
        $message .= sprintf(__('Username: %s'), $user_login) . "rnrn";
        $message .= sprintf(__('E-mail: %s'), $user_email) . "rn";

        @wp_mail(get_option('admin_email'), sprintf(__('[%s] New User Registration'), get_option('blogname')), $message);

        if ( empty($plaintext_pass) )
            return;

        $message  = __('Hi there,') . "rnrn";
        $message .= sprintf(__("Welcome to %s! Here's how to log in:"), get_option('blogname')) . "rnrn";
        $message .= wp_login_url() . "rn";
        $message .= sprintf(__('Username: %s'), $user_login) . "rn";
        $message .= sprintf(__('Password: %s'), $plaintext_pass) . "rnrn";
        $message .= sprintf(__('If you have any problems, please contact me at %s.'), get_option('admin_email')) . "rnrn";
        $message .= __('Thanks!');

        wp_mail($user_email, sprintf(__('[%s] Your username and password'), get_option('blogname')), $message);

    }
}