I am not sure if I understand what you mean with multi-file and why it matters. As a lisp, the program is already in memory, I can interact with it through the repl. I am sure I can ask it to format itself?
If the program has syntax errors, nothing can happen, how would it know how to format it self if it is not correct?
Perhaps the approach is very different in lisp (and smalltalk which I have some experience with), there is no parsing of the program from the outside - or - if you take that approach and treat the s-expr as dead text you have to sort of reimplement the parser (or the system) in order to have some understanding of it, which in my mind seems very inefficient.
Why can you not just give macros enough meta-data so the reader-formatter knows what kind of formatting the form desire? Provided your lisp have macros of course...
Funny how much complexity you have to introduce by just getting rid of the parentheses.
I later learned that MLISP functioned as a preprosessor for a normal lisp. Don’t know about the macro facilities, perhaps someone can chime in with details?