Yes, your modification/approach sounds good.
I haven't looked into local hosting of comments for a couple of years, but Hypothes.is is FOSS and IIRC it is possible to run your own service if this is important. I'm not aware of anyone who has done this. There may be other tools/services that you could work. Overall we're attempting to avoid reinventing the wheel, and commenting tools are already very common -- e.g. Disqus, Commentics, etc. Our own commenting tools were lacking major features like a proper moderation/administration tool, so we decided that integration rather than reinvention was a better approach.
Public Knowledge Project Team