<?php 

add_filter( 'pre_comment_approved', function( $commentstatus, $commentdata ) {
    $commentstatus = 0;
    return $commentstatus;
}, 10, 2 );

add_filter( 'wp_update_comment_data', function( $data, $comment, $commentarr ) {
 
    if ( isset( $data['comment_approved'] ) ) {
        $data['comment_approved'] = 0;
    }
 
    return $data;
 
}, 99, 3 );