Second response (to your now edited post):
Yes, notes seem to be underdeveloped. I keep bringing up the scrolling issue that nobody at Medium seems to want to address. Get too many in a row, and just try to scroll. They disappear!!
As for your question: If responses are posts, why aren’t notes posts? This is a good question. I’ve seen this thing:
However, when you click it, NOTHING SEEMS TO HAPPEN. Is this future functionality?? I’d like to know. A shareable link would seem to suggest some way of embedding, but if the original author can hide visibility and even delete, what happens then?? These are good questions, Timothy.