Proposed resolution (June, 2013):

Change 12.2.4.3 [over.ics.rank] paragraph 4 as follows:

...Two conversion sequences with the same rank are indistinguishable unless one of the following rules applies:

• A conversion that does not convert a pointer, a pointer to member, or std::nullptr_t to bool is better than one that does.

• A conversion that promotes an enumeration whose underlying type is fixed to its underlying type is better than one that promotes to the promoted underlying type, if the two are different.

• If class B is derived...