The talk by Sid Kasuvajhula is an absolutely fascinating presentation about extremely flexible object-oriented interfaces, organized in a multi-hierarchial manner -- so very nicely exploiting the compositional structure inherent in the content we operate on.
Wow. This is so cool. Sometimes you come across concepts that makes total sense once you know it, but then keep asking yourself why wasn't it discovered way before. This a great example of that.
Epistemic mode, A scalable UI paradigm https://emacsconf.org/2020/talks/07/