Jim> Having a global "R4RS mode" won't really work, because most
Jim> code is written to expect either one behavior or the other.
Can I argue for just a minute longer?
Packages written to have #f and () identical have not yet been
written, and the will be specific to Guile, and will probably all be
from translating packages (which don't yet exist).
So R4RS could be the default behaviour, and then you could say
(guile-false-nil-mode #t) in your translator to turn it on.
Then the Guile manuals would say that when you write a translator from
a lisp dialect that treats nil == (), you have to set that mode.
I don't see a problem with this idea.