Blog comments = Disqus + Jekyll29 Jun 2015
Jekyll and Disqus integration steps are described in Joshua Lande's post.
However it is better to get a little bit deeper and set Disqus configuration variables.
It's pretty simple and straightforward. Quote from my layout:
Variable gamladisqussatte is needed for the old-style Disqus comments (integrated without setting variables other than disqus_shortname) not to be lost. It is set in the post's YAML frontmatter.