Disqus replaces the div on page load, then loads the comments asynchronously.

I have Disqus on my Jekyll/Octopress blog and still get millisecond loads.

I intended to type this ;-)

Still, Disqus has basically a no/low-impact

Agreed I moved my blog from Rails to static. I tested pageload speeds with disqus on/off and the differences were negligible.

Disqus loads almost entirely async.