Proposed resolution:

Replace [locale.codecvt.virtuals] paragraph 11 with the following:

Returns: The maximum value that do_length(state, from, from_end, 1) can return for any valid range [from, from_end) and stateT value state. The specialization codecvt<char, char, mbstate_t>::do_max_length() returns 1.

The text of codecvt::do_max_length's "Returns" clause (22.2.1.5.2, paragraph 11) is garbled. It has unbalanced parentheses and a spurious n.