I want my websites to be more interactive but if people can submit comments using a form, I don't want the same person to be able to submit any number of comments at a given time.

It would take someone with too much time on their hands to make your site trashy looking with 200 comments of garbage, but I'd still prefer to have some automatic control over php forms.

I don't want to buy anything, or use Wordpress as a blog (they charge you $99 a year or something just for full customization! WP must be a rip off)

With this kind of thing, it would be tricky to know what exactly I should search for in Google. I get tired of being directed to sales pages when I search for such things...