The comment form is implemented as a server-side program using Common Lisp and Hunchentoot. So this is the only part of the website that is not static. The server-side program accepts each comment and writes to a text file for manual review. Then I review the comments and add them to my blog.
In the end, the comments live like normal content files in my source code directory just like the other blog posts and HTML pages do. My static site generator renders the comment pages along with the rest of the website. So in effect, my static site generator also has a static comment pages generator within it.
The next time I rebuilt the blogs the page "XXX" would render a loop of all the comments, ordered by timestamp, if anything were present.
The CGI would send a "thanks for your comment" reply to the submitter and an email to myself. If the comment were spam I'd just delete the static file.
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I find this method to be a sweet spot between generating content on your own pace, while allowing other people to "post" to your website, but not relying on a third-party service like Disqus.