This is a proof-of-concept plugin that creates a simple comment thread on any static Cloudflare Pages site. This uses Cloudflare's D1 Database Service which is currently in ALPHA and should not be used on important production sites.
I'm using this on my own site and also have a demo hosted at https://simple-cloudflare-commentes.pages.dev.
Once you've got the Cloudflare bits working, you can add comments to a website with something as simple as
<div id="comments"></div>
<script>fetch('/scc/comments').then(response=> response.text()).then(text=> { document.getElementById('comments').innerHTML = text; if (location.href.includes('#')) location.href=location.href;});</script>
Full set-up instructions can be found here.