wp_trash_comment

 * The comment is moved to Trash instead of permanently deleted unless Trash is
 * disabled, item is already in the Trash, or $force_delete is true.
 *
 * The post comment count will be updated if the comment was approved and has a
 * post ID available.
 *
 * @since 2.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param int|WP_Comment $comment_id   Comment ID or WP_Comment object.
 * @param bool           $force_delete Whether to bypass Trash and force deletion. Default false.
 * @return bool True on success, false on failure.
 */
function wp_delete_comment( $comment_id, $force_delete = false ) {
	global $wpdb;
	$comment = get_comment( $comment_id );
	if ( ! $comment ) {
		return false;
	}

	if ( ! $force_delete && EMPTY_TRASH_DAYS && ! in_array( wp_get_comment_status( $comment ), array( 'trash', 'spam' ), true ) ) {
		return wp_trash_comment( $comment_id );
	}

	/**
	 * Fires immediately before a comment is deleted from the database.
	 *
	 * @since 1.2.0
	 * @since 4.9.0 Added the `$comment` parameter.
	 *
	 * @param int        $comment_id The comment ID.
	 * @param WP_Comment $comment    The comment to be deleted.
	 */
	do_action( 'delete_comment', $comment->comment_ID, $comment );

	// Move children up a level.
	$children = $wpdb->get_col( $wpdb->prepare( "SELECT comment_ID FROM $wpdb->comments WHERE comment_parent = %d", $comment->comment_ID ) );
	if ( ! empty( $children ) ) {
		$wpdb->update( $wpdb->comments, array( 'comment_parent' => $comment->comment_parent ), array( 'comment_parent' => $comment->comment_ID ) );
		clean_comment_cache( $children );
	}