"If unquote adds a '', then `,'foo should return ''foo, right?"
Unquote doesn't add '', @ does. Perhaps that changes your example?
"In any case, there's no reason foo should be called, is there? O_o"
:) Yeah that's a bug with my paren inference; it was implicitly wrapping the expression in parens. I'd never seen backquote-comma before. Here's a temporary workaround:
wart> (list `,(write `,'foo))
foo(foo) ; ignore the (foo) -- it's the return value
