I'm a fan of Discourse. That should come without surprise at this point. As a fan, it's natural for me to see the potential for Discourse to solve communication problems and create selective visibility within an organization. So it was easy for me to gravitate toward it for the IT communication structure at my church.
For years, Disqus has been the commenting platform of choice. It's what I used when my site was on WordPress. When I switched to a static site generated by Jekyll, I pulled commenting entirely. But given the topics I write about, comments can be quite helpful and I realize that was a mistake. So I brought them back with the help of Discourse.