Danyl, sorry I hadn’t seen your response until now. I don’t spend much time on Medium and don’t see notifications from it.
I’m all-in on the IndieWeb philosophy of POSSE (Post to your Own Site, Syndicate Elsewhere), so all my content originates on my personal site and is syndicated out, typically to reach friends, family, and additional audience. Most platforms I syndicate to, I have means of getting responses backfed to my site using Webmention to provide notifications of interaction. Sadly Medium doesn’t play nicely on this front.
I watch a lot of this space pretty closely and know most of the programmers and players in the space. HongPong, who you link to, I know more as a Drupalista than a WordPresser. The OStatus/AP related plugins you’ve linked to are from Mathias Pfefferle who is one of my favorite programmers and my personal site relies on quite a bit of his work.
One effort you have missed which is very interesting is Ryan Barrett’s Fed Brid.gy effort which is well worth looking at for it’s ability to work across multiple platforms and bridge the worlds of IndieWeb and Activity Pub protocols.