"...then I'd say a single item should be put in a list too [...] And yet now Nuit values at the root can't be strings; they must be lists."
That's correct. There's an implied list wrapping the entire Nuit text. You can think of it like XML's root node, except in Nuit it's implicit rather than explicit.
Calling "readfile" in Arc also returns a list of S-expressions, so this isn't without precedent.
