I suppose this comes up a lot, I'm searching past discussions. I think I may just have a little code written to accomplish. If I post a URL to an example web site/page, can someone comment?
Yes, it does come up frequently on various forums, but people do not often reply as it does require a knowledge of a server-side language and database code.
(You could look at this - http://www.cellbiol.com/scripts/free_php_guestbook/free_php_guestbook.html).
Basically you would require your comment form to send the info to a database and then be included in your page using the sql WHERE clause to decide if the comment should be included depending on if you wish to 'approve' the inclusion or not.
In addition to the link PZ provided, you might find what you need at Gentle Source under PHP Guestbook or PHP Comments scripts. http://www.gentlesource.com/
You definitely need an admin area to edit/delete unwanted posts. These kinds of things are magnets to spam bots.