REST just says that you should conform to the uniform interface. In other words, it says you should do what POST is supposed to do as per the HTTP spec. Here is the quote from that spec that is relevant,
If a resource has been created on the
origin server, the response SHOULD
be 201 (Created) and contain an entity
which describes the status of the
request and refers to the new
resource, and a Location header
(see section 14.30).
As you can see from this, you have two places where you can indicate to the client where the newly created resource resides. The Location header should have an URL that points to the new resource and you can return an entity with the details also.
I’m not sure what the difference between overriding acceptRepresentation() and overriding post() but this example shows how to return a response from a POST.