[Voted into the WP at the March, 2011 meeting as part of paper N3262.]

According to 14.4 [except.handle] paragraph 16,

The object declared in an exception-declaration or, if the exception-declaration does not specify a name, a temporary (6.7.7 [class.temporary]) is copy-initialized (9.4 [dcl.init]) from the exception object. The object shall not have an abstract class type. The object is destroyed when the handler exits, after the destruction of any automatic objects initialized within the handler.

This wording leaves unspecified how an exception-declaration that is a reference should be treated. For example, presumably a reference to an abstract class type should be permitted, but that is not specified. The treatment of ellipsis is also not clearly addressed.