Because, as I said above, the number
of functions requiring a very strict stack discipline
(stricter than the valid/acceptable index requirement) is
not large, I think it would be good to document that
explicitly. Even if that does not prevent making those
mistakes, it will be much easier to understand that it is
indeed a mistake and require no research as to whether this
is a mistaken use of the API or a bug in Lua.
Probably we have already spent more text discussing adding that note
than it would take to add it, which personally is my usual threshold
for "go ahead and add it". :-)