This looks really solid! I will include it in my blog post [0], where I evaluate many different ways and tools to integrate comments on a static site.

I really like that you provide a free plan, but I don't understand, why your pricing depends both on bandwidth and monthly comments published. I would also prefer a flat comments-per-month plan, so I didn't have to pay extra 5$ if I get 51 comments in a single month.

[0] https://darekkay.com/blog/static-site-comments/