Since you ask, Roland, I think free commenting platforms are overrun because of the fundamental asymmetry between the energy it costs to make a mess and the energy needed to clean things up. Increasing entropy is always easier than decreasing it. This introduces a power difference in favour of the trolls. Such differences can be lessened somewhat by things like making services paid, or by using less mainstream services (how you use GitHub), better yet self-hosting, or other things that mean an additional cost for entropy-spreaders. Which is why I host my own comments and use outside help only to weed out those commenters that leave additional entropy in their wake (one of the things it does is make the cost lower for known commenters, than for others). Which is also why I’m answering here, and not on GitHub as you suggest. (And hopefully you have something like Webmention enabled so you’ll know)
thank-you! i read your blog by RSS so I don’t need Webmention
you are 100% right about entropy and power differential!