Proposed resolution:

In [facets.examples] paragraph 13, insert "const" in two places:

string do_truename() const { return "Oui Oui!"; }
string do_falsename() const { return "Mais Non!"; }

In [facets.examples] paragraph 13, the do_truename() and do_falsename() functions in the example facet BoolNames should be const. The functions they are overriding in numpunct_byname<char> are const.