On the French Wiktionary, I notice occasional odd sort glitches. For instance, http://fr.wiktionary.org/w/index.php?title=Cat%C3%A9gorie:Noms_communs&subcatfrom=bok%0ANoms+communs+en+bok#mw-subcategories will show "Noms communs en bokobaru", "Noms communs en boko", "Noms communs en bokyi" despite the fact that the first two sub-categories are indexed with Catégorie:Noms communs|bokobaru and Catégorie:Noms communs|boko, respectively. The few times this happens, it is always the case that the out-of-sequence sort key is a prolongation of the key it should go after.
Another particularly bad example is http://fr.wiktionary.org/w/index.php?title=Cat%C3%A9gorie:Noms_communs&subcatfrom=dan%0ANoms+communs+en+dan#mw-subcategories where we have danaru, dangaléat, dani de l’Ouest, dani de Mid Grand Valley, danois, dano, and only then dan (so we have dan moved down six slots, and dano moved down one slot).