Proposed resolution:

This wording is relative to N4606.

1. Edit [list.ops] p29 as indicated:

   void sort();
   template <class Compare> void sort(Compare comp);
   

   -28- Requires: operator< (for the first version) or comp (for the second version) shall define a strict weak ordering ([alg.sorting]).

   -29- Effects: Sorts the list according to the operator< or a Compare function object. If an exception is thrown, the order of the elements in *this is unspecified. Does not affect the validity of iterators and references.

   […]

[ 2017-01-27 Telecon ]

Priority 0

Sometime between N1638 and N1804 the sentence "If an exception is thrown the order of the elements in the list is indeterminate." in the specification of list::sort went missing. This suspiciously coincided with the editorial change that "consolidated definitions of "Stable" in the library clauses" (N1805).

forward_list::sort says that "If an exception is thrown the order of the elements in *this is unspecified"; list::sort should do the same.