I guess having some script on your html pages where people can post their comments is good, because it adds new content to the page and keeps if "fresh and s3xy" for the search engines, as I like to say. I assume the comments would usually be topic related, and I assume that all links should be no-follow, otherwise it would get flooded by hungry SEOers. But then it would probably need to be moderated to cut out vulgar additions etc. Just wondering if you think the exercise is worthwhile, and if you know of any free scripts that I could use for this.
You could check out http://www.hotscripts.com/ for some scripts there. Their website is full of them and supplying them is what their service is so you should find just what you need. I would reccommend it, providing that you had some form of moderation there. Best of luck, ~ Mike
Comments are good for any site that publishes articles/news/reviews etc.. For a regular visitor it provides a way to interact with the writer/business. Nofollow for links in comments is good if you want to stay away from spam.