Thecomment_max_links_url 过滤我们可以计算评论内容中的内部链接数量，并从中找到的链接总数中减去该数量($num_links), 在以下过滤器的帮助下check_comment() 核心功能：

/**
 * Filters the number of links found in a comment
 *
 * @since 3.0.0
 * @since 4.7.0 Added the `$comment` parameter.
 *
 * @param int    $num_links The number of links found.
 * @param string $url       Comment author\'s URL. Included in allowed links total.
 * @param string $comment   Content of the comment.
 */
 $num_links = apply_filters( \'comment_max_links_url\', $num_links, $url, $comment );

核心仅统计<a> 标签，包含href 属性，具有：

$num_links = preg_match_all( \'/<a [^>]*href/i\', $comment, $out );

演示插件-允许来自主url主机的链接这里有一个示例，允许评论内容中的任何内部链接：

/**
 * Allow any internal links from the home url host, in the comment\'s content
 *
 * @see http://wordpress.stackexchange.com/a/257917/26350
 */

add_filter( \'comment_max_links_url\', function( $num_links, $url, $comment )
{
    // Allowed hosts
    $allowed_host = wp_parse_url( home_url(), PHP_URL_HOST );

    // Get all links
    $all_links = preg_match_all( 
        \'/<a [^>]*href=["\\\']([^"\\\']+)/i\', 
        $comment, 
        $links 
    );

    // No links
    if( empty( $links[1] ) || ! is_array( $links[1] ) )
        return $num_links;

    // Count links that are from our home url domain
    $internal_links = array_reduce( 
        $links[1], 
        function( $internal, $link ) use ( $allowed_host )
        {   
            if( $allowed_host === wp_parse_url( $link, PHP_URL_HOST ) )
                $internal += 1;

            return $internal;
         },
         0 
    );

    return ( $num_links - $internal_links );
}, 10, 3 );

演示插件-允许来自多个主机的链接这里有一个允许多个主机的示例：

/**
 * Allow any internal links, from multiple allowed hosts, in the comment\'s content
 *
 * @see http://wordpress.stackexchange.com/a/257917/26350
 */

add_filter( \'comment_max_links_url\', function( $num_links, $url, $comment )
{
    // Allowed hosts
    $allowed_hosts = [ \'foo.tld\', \'bar.tld\' ]; // <-- Adjust to your needs!

    // Get all links
    $all_links = preg_match_all( 
        \'/<a [^>]*href=["\\\']([^"\\\']+)/i\', 
        $comment, 
        $links 
    );

    // No links
    if( empty( $links[1] ) || ! is_array( $links[1] ) )
        return $num_links;

    // Count links that are from our allowed hosts
    $internal_links = array_reduce( 
        $links[1], 
        function( $internal, $link ) use ( $allowed_hosts )
        {
            if( in_array( wp_parse_url( $link, PHP_URL_HOST ), $allowed_hosts, true ) )
                $internal += 1;

            return $internal;
         },
         0 
    );

    return ( $num_links - $internal_links );
}, 10, 3 );

我们曾经array_reduce() 和wp_parse_url() 帮助计算上述插件中的内部链接或来自允许主机的链接。

请进一步测试并根据您的需要进行调整