All who miss a 'normal' guestbook function in Turtle, are suspicious with social media like Facebook, Twitter etc. and publish their albums on local host providers, may be perhaps interested in a very easy and quick solution. Nearly each host provider offers PHP, so it's not a great deal to embed a PHP guestbook in your Turtle album. I've gladly discovered 'myPHP Guestbook 4.6.2' on https://www.php-guestbook.de/ two days ago and after an intense study of the enclosed 'readme' file, I've managed to provide my webspace with PHP 7.0 and created my first SQL database on my providers server. All you have to do is to load up all the guestbook files on your webspace, surf to the install folder and start the script-controlled installation.
After that, I've created an empty page in Turtle and integrated the given java script code from the 'readme' file in the page's header and enclosed the guestbook call via <iframe> in the page's body. Nothing easier than that! Using the admin access to your guestbook lets you choose between ten templates, which can be adjusted to fit to your individual site design.
The only disadvantage for the english speaking user majority is the german language of the 'myPHP Guestbook'-site. But the downloadable ZIP-file contains an english 'readme' and you can choose the installation of an fully english version (german and english only!). I assure you, that I've nothing to do with the software's manufacturer! I'm just so impressed by the simplicity and functionality of this software that I want to share my enthusiasm . Here you can see how it looks: http://bernis-bilderwelt.de/gaestebuch.html (still empty, because the site is new and the guestbook online since yesterday...).