Remove Code from Guestbook v2.3.1

Can someone tell me where I would find the code for the "add comments" feature in the guestbook. Most of the spam I get on my book is placed as a comment to an existing entry so I'd like to remove that option from the guestbook however I don't know where to find that code or exactly what code to remove. I've already replaced the icons with an image of the background colour so you can't see where the "add a comment" icon is and it helped a little.

If removing the code is difficult and/or could cause problems, would it be possible to add human verification code to "add comments" section. I found human verification code here some time ago (I think the code was provided by carbonize) which helped a lot with cutting down on spam in the new entries of the guestbook.

Turn on the password as found in General Settings.

Thank you. Talk about a D'OH!!!!!! moment.