A little while ago (on 19 October, to be precise) someone mentioned commento.io, an open source commenting system for websites. It looked interesting, so I tried to leave a comment on the post that mentioned it. Despite a few problems with login, I managed it, and asked whether Commento could play nicely with webmentions. No reply there, but I also took the matter up with support at Commento.
Today I got a reply. It didn't really address the login point, but did speak to Webmentions:
There’s more ➢