This is a WordPress blog - it's just a matter of installing the SuperCache plugin and turning on mod_rewrite caching - then all page requests are served by apache out of static files. It even handles regeneration when there's a new comment, while continuing to serve the old static file to avoid the thundering herd problem.
Only if you are comfortable using a 3rd party comment service (or injecting 3rd party javascript in your site in the first place). I know it's common, but even with the advances in CORS and whatnot, it still (IMNHO) defeats a lot of the benefits of a static web site.
That said, I would probably prefer embedding disqus or https://muut.com/ comments to running a complex php application just for comments.
The crucial flaw of public comments is that they can be used to address other people than the author; hence spam and trolls for instance. And what's the ratio of actually useful comments anyway? Does it justify the cost of dealing with all the rest (like, say, your blog going down because some comment DB broke which directly hurts your actual readership)?
One-way communication has its advantages, too. Those who really have something to tell you can always use email.