To the point:
Your message structure will need to have at least one item for each of the tasks you are talking about:
Article number
(number is best, you can do this other ways, but number are best for future use)
Possible user number
(this is helpful if you start having user login, or want to be able to delete all the spam that is going to hit yoursite once you open up a form comment system)
comment number
(the number of the actual comment, so you can add delete modify it in the future)
article address might be handy
(this is assumeing that you are attemping to integrate this into a "static" or non-database drive site you already have.
So then you need multiple tables, the reason for this is that you are going to be creating "one to many" relations ships. Many comments, to one article, or one user.
It is a lot of fun to do database stuff, and if you are just getting your feet wet then I disagree with the above post, and say go for it! However, if you are in a hurry, then just use a CMS like Joomla or Drupal, or a thousand others. (content management system)
When I was getting started sometimes I would download apps that did similar tasks, and look at their data structures for ideas.
Good luck, get some more books, but nothing with idiot or dummy in the title, it is bad for moral,
-- Will