Thanks for the pointer. He has an entire chapter on hygiene... And then there is this:
"There is no need to provide quotation here because, having failed to enforce the prohibition against embedding combiners in a macro expansion, we don’t need to embed their unevaluated names in the expansion."
It's nice that his primitive $vau grabs the current lexenv, as this enables another kind of macro-like behavior I've thought might be useful: taking subexpressions, fully macroexpanding them, and doing something with the result (e.g. determining whether a variable is ever used, and omitting a computation if not). I don't know how that would mesh with the interpreter's semantics, though...
I'll probably have to read and brood on this further.