I really liked Colin Walker’s point:
Until Indieweb support is baked into core WordPress isn’t going to be the answer but there seems to be a reluctance to go this route.
Needing to manually ping other sites is not going to achieve that.
I collected some thoughts and reflections on my own tribulations here. I am just confused why the mentions are not even coming through to my spam? What is even more confusing is when I tried to manually add your comment to my ‘Co-claiming’ post, it gave me an error. Who knows what is going on. Maybe the error log has something, not sure.