It only works if you check the box that says you are a person, it has worked this way for a long time.
This is a low fi way to avoid comment spam from scripts.

Joe

Blog comments allow anonymous posting therefore its a little effort to reduce comment spam generated by scripts. I should probably do something also for the contact form but I've never had spam from there. I've only had a little spam in the blog and thats when I added the checkbox.

Yes a check box is easy for scripts to solve and eventually we will have to do something better but so far comment spam has not been a big problem so the simple solution is ok. I'm not a big fan of captcha techniques and in more popular blog software captcha has only worked part of the time and made things more difficult for users often. I think surely a check box is easier for users than captcha so I use that until it no longer works then I will implement something else. Maybe captcha or maybe random math problems like in this blog or whatever I can find that works and is least difficult for users.

In my testing it does not lose the comment if the user does not check the box, it simply does not process the input, the user can check the box and post the data after realizing their mistake.

It says right there "You must check this to post your comment"

Joe

I recently had a user report to me that they were getting 300+ comment spams a day in their blog so apparently there are scripts that have figured out the simple "I am a Real Person" checkbox that we were using to prevent comment spam.

So I have implemented a simple math question that the user must answer in order to post as a little stronger defense.

This is available in svn branches/2.x

I added a module setting for whether to use the SPAM blocker question or not and also added a module setting to disable blog comments.

I added a similar option to the Contact Form module since it typically also allows anonymous posts.