protected function idOrEmailToId( $id_or_email ) {
		if ( is_a( $id_or_email, WP_Comment::class ) ) {
			return intval( $id_or_email->user_id );
		}

		if ( ! is_numeric( $id_or_email ) ) {
			$user = get_user_by( 'email', $id_or_email );
			if ( $user ) {
				return intval( $user->ID );
			}
		}

		return strval( $id_or_email );
	}