Looking at Notes, I get why Elon is so mad about it. They totally ripped off the Twitter UI. I follow Ed Zitron's Substack, and he is also a prolific Tweeter. He seems to be using Notes the same way he uses Twitter, for shitposting. I'm not sure that's really in line with the tone of Substack.
I actually thought that a newsfeed would be a good fit for substack, but looking at this i dont think i m going to use it. It should be simpler, a timeline of things i ve subscribed, with some threaded, sane comments. The medium shapes the message, and twitter's medium is just not a good fit for substack's message