Anti-spam feature: IP limits?

https://mookitty.co.uk/devblog/
Check out Kitten’s Spam tools. They are excellent, and you can use them to quickly and easily add IP addresses, keywords, and email addresses to the spam words list.

That looks helpful, but doesn’t offer the feature I was talking about. What I want is a set limit on the number of comments any one IP can post.
The scenario: While I’m out of town, a spammer tries to post 2,000 comments. Their first 5 post just fine (unless another spam tool catches them) and the rest are automatically blocked.

Set that if a single link is put into a comment, then the comment automatically goes into moderation.
You could restrict repeat comments by having a time limit, but otherwise, I really would use Kitten’s plugin.
Is a person is doing it, once they see that they are having no effect, they will move to another blog.
Kitten’s plugin also makes it very very easy to mass delete and then block that IP etc.
https://photomatt.net/2004/08/13/tramadol-attack/

Actually it looks like WP is a step ahead of me. From wp-comments-post.php:

// Simple flood-protection
$lasttime = $wpdb->get_var("SELECT comment_date FROM $tablecomments WHERE comment_author_IP = '$user_ip' ORDER BY comment_date DESC LIMIT 1");
if (!empty($lasttime)) {
$time_lastcomment= mysql2date('U', $lasttime);
$time_newcomment= mysql2date('U', $now);
if (($time_newcomment - $time_lastcomment) < 10)
die( __('Sorry, you can only post a new comment once every 10 seconds. Slow down cowboy.') );
}
So setting this to every 5 minutes or so instead of 10 seconds would put a serious crimp in these attacks…

You could also add Comment Preview.
https://weblogtoolscollection.com/archives/2004/05/20/coment-preview-for-wordpress-12/
I think the thing about an individual site is to just make another site look more attractive for the people that do this.