Many people use Disqus as a commenting system for their (static) blog. It’s a free service, easy to get started with, and it has everything you’d expect from a commenting system. It’s free up to the point where Disqus decides to show advertisements alongside the comments, and these advertisements are so bad, you will look for better options very quickly. The way out of advertisements, of course, is to start paying for their services. Actually, I would have paid already for their service, if only they would have reduced the tremendous amount of stuff they load on your page. And the cookies they need for tracking you across the internet of course.