Note: this solution just worked for half a day and was defeated. I worked out another solution: A simply way to block spam comments on WordPress (2)
Change the 20th line of the file wp-comments-post.php in the root folder:
$comment_post_ID = isset($_POST[‘comment_post_ID’]) ? (int) $_POST[‘comment_post_ID’] : 0;
to:
$comment_post_ID = isset($_POST[‘comment_post_ID_iblog‘]) ? (int) $_POST[‘comment_post_ID_iblog‘] : 0;
Change the 1144th line of the file “wp-comments-post.php” under the “wp-includes” folder:
$result = “<input type=’hidden’ name=’comment_post_ID’ value=’$id’ id=’comment_post_ID’ />\n”;
to:
$result = “<input type=’hidden’ name=’comment_post_ID_iblog‘ value=’$id’ id=’comment_post_ID’ />\n”;
This solution just works for half of a day. I have another solution.