What I just tried was adding the giscus JS into a <script....> tag into my README.md - that would have created a comment box in my readme on flows.nodered.org - but of course, <script> tags aren't allowed, so nothing got rendered.
Just as background, giscus uses github logins to allow people to comment. These comments are stored as discussions on repositories (of ones own choosing) - so the discussion feature has to be activated on the corresponding repository. It's nice since no - paid - storage is required, no payments and users have to be logged into GitHub - no spam. But also no comments because which user is going to be logged into GitHub 
It would be a simple solution to the comment part of this discussion but it would require flows.nodered.org to allow the rendering of third party scripts. Or perhaps some "meta" YAML at the top of a readme.md files would automagically trigger the rendering of giscus comments...
(just thinking out loud)
