"Speaking of which, it seems like there will always be exactly one unindented line in Nuit's textual encoding, that line being at the beginning. Is this true?"
Well, not exactly. If all the lines are blank, that's fine too. But assuming at least one non-blank line... there must be at least one line that is unindented. There might be more than one unindented line.
"...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.
