Rationale (04/00):

1. Replacement deallocation functions are already required not to throw an exception (cf 16.4.5.8 [res.on.functions] paragraph 2, as applied to 17.6.3.2 [new.delete.single] paragraph 12 and 17.6.3.3 [new.delete.array] paragraph 11).
2. Section 16.4.5.6 [replacement.functions] is describing the signatures of the functions to be replaced; exception specfications are not part of the signature.
3. There does not appear to be any pressing need to require that class member deallocation functions not throw.