Comment spams
The nice thing about an NIH comment post thing is that you can change it if people start to abuse it.
I was starting to get more and more comment spams. Some spammer obviously must have taken a look at my comment submission form, and written some code to post his junk there. Even though they made a little mistake that would make it very easy to identify their posts (URL-encoded the data in some field where it was not necessary, and indeed would mean that the post would not be visible had I approved it), I didn't feel like adding much code to special-case one particular spammer.
So instead, I changed my comment form to rename a particular field,
and would return a 403-style rather empty page with a remark of Sod
off, spammer
if the field is filled in. When I start to receive spam
again, changing the code to do the same thing once more is pretty
easy.
It's been a few weeks now. And I didn't have to change anything about my comment submission policy, like some other people had to do.
Isn't that nice? 
You are lucky, I don't have this chance.
In order to protect my blog from spam comments I did the following :
1) Adding a false "website" field, hidden by the CSS. If the field is not "http://", the default value, the comment is refused.
2) The encoded name of my "Name" field is a obscur letter-number 12a8s56 that change every week. This field must be completed. If not, the comment is rejected.
3) Another hidden field, that has nearly the same name as the "Name" field. It also change every week and the comment is rejected if this field is not empty.
Despite all of this, I still receive 20-30 spams comments every days. I don't know how the hell they are doing this. I cannot imagine a robot that can spam my blog !!
If I hadn't all those things, I would receive a lot, really a lot. (I desactivated my trackbacks spam detector one night, in the morning I had 190 trackbacks spam ! Once, I was working on my comment filter and it was not activated for 5 minutes : I received 3 spams comment in 5 minutes !)
I said '403-style', not '403'
I'm not actually giving them a 403; the reason I mentioned this in my post is to make people understand what the idea is. In reality, I'm using PHP's die() function to say "Sod off"