Setting up comments in Simply Static is simple, as most heavy things are done in the background.
Activate comments
Go to Simply Static -> Settings -> General->Forms and scroll down to the Comments section.

Add a redirect URL
You want to add a redirect URL to automatically redirect your users once they’re submitted a new comment to a post. That’s because there is quite a lot happening in the background, and you don’t want your users left confused after submitting a comment.
What happens in the background
Simply Static sends the comment to your WordPress website and submits it via the internal comments function called wp_insert_comment(). Depending on your WordPress comment configurationThe setup process where you specify the settings and options for how a software or system will operate., it will be immediately published or left for review.
Simply Static will automatically create a new static exportThe process of saving the files and data from your WordPress site to create a static site. for the post after the comment was published to make it available on your static website.
Instead of using a JSONJavaScript Object Notation. A lightweight format for storing and exchanging data. configuration file, comments work with JavaScriptA programming language used in web development to create interactive elements on a webpage. and use a meta tag on your static website to get all the information needed.