>And a secretary is a medium.

Not in McLuhan's use of the word. His examples are all pieces of technology that extend our senses; another person helping you do something is not a medium.

I'm not saying you are wrong about the word "medium" in general, but simply that McLuhan had a very specific usage of the word that is not the same as the lay meaning and includes things like light bulbs, numbers, and money. The more modern usage of the word to generically refer to sources of information is very different. In that sense, AI is media insofar as it's feeding us content and information, but it does not meet the specific (and more interesting IMO) definition McLuhan put forward in Understanding Media. Obviously, others can and will disagree with me there, but I simply don't view LLMs are an extension of our thought. Things like the internet, encyclopedias, the education system, etc., are McLuhan-esque media of thought extension, whereas LLMs actually serve the opposite purpose. They abridge rather than extend it by doing it for you.

This arguably is more interesting than yet another closed messaging platform, but still not gonna use it with this requirement in place.