As some others have already hinted, this sounds a lot like Emacs with Org-mode. Also, who writes such testimonial snippets? The style of writing doesnt make me particularily trust they are real :-)
It's not really like org-mode, but similar. The big difference is that org-mode has inline-folding, while leo breaks up and recreates documents on loading/saving-time. Inside the app, leo has better performance because of this, and potentially less problems with folding-syntax. It's also quite easy for leo to allow hard and soft linking in it's document-tree. With org-mode this is only possible through ugly hacks.
Org mode has the ID property, you can implement soft linking with them.
Yes, you can, but it's still an ugly hack. Or is org-mode now capable of live-updating the linked segments?