Wow, this is pretty awesome! I really like the idea of tooling moving out of editors, into libraries that can then be easily integrate into automated tools (reformatting, type checking, scope info, etc.), and of course rendered in editor.
It also allows projects/languages like this to get a lot of benefit without boiling the ocean. A bit similar to Clojure's hosted-language approach in that regard.
I used Hy in a Django project to define the URLs. I was using some functions that added input checking, and I wanted to parse that and generate Javascript functions that would check the input in the client. Hy takes less effort to parse than Python (just call read).
It also allows projects/languages like this to get a lot of benefit without boiling the ocean. A bit similar to Clojure's hosted-language approach in that regard.