Anti spam measure: Remove all links in WordPress comments when the comment form is being submitted, using a filter hook

listing-18-14.php

function wh_remove_comment_links( $content ) {
    global $allowedtags;
    $tags = $allowedtags;
    unset( $tags['a'] );
    $content = addslashes( wp_kses( stripslashes( $content ), $tags ) );
    return $content;
}
add_filter( 'pre_comment_content', 'wh_remove_comment_links' );