Comments blocked by the blocklist should be spam and not trash. Companion plugin for Antispam Bee.

blocklist-to-spam.php

<?php
/**
 * Plugin Name: Blocklist to spam
 * Description: Comments blocked by the blocklist should be spam and not trash.
 * Plugin URI:  https://torstenlandsiedel.de
 * Version:     1.0
 * Author:      Torsten Landsiedel
 * Author URI:  http://torstenlandsiedel.de
 * Licence:     GPL 2
 * License URI: http://opensource.org/licenses/GPL-2.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly.
}


/**
 * Comments blocked by the blocklist should be spam and not trash.
 *
 * @param int|string|WP_Error $approved    The approval status. Accepts 1, 0, 'spam', 'trash', or WP_Error.
 * @param array               $commentdata Comment data.
 * @return int|string|WP_Error             The approval status. Accepts 1, 0, 'spam', 'trash', or WP_Error.
 */
function move_blocklist_from_trash_to_spam( $approved, $commentdata ) {
	// If the approval status is trash, then change to spam.
	if ( 'trash' === $approved ) {
		$approved = 'spam';
	}

	return $approved;
}
add_filter( 'pre_comment_approved', 'move_blocklist_from_trash_to_spam', 10, 2 );