"handles" in what sense? It needs to give different answers for the same letter depending on whether the text is English or Turkish, for example, so I don't se

"handles" in what sense? It needs to give different answers for the same letter depending on whether the text is English or Turkish, for example, so I don't see how it can "handle" it in general. Reading the documentation you link to, the answer in the fine print is that fc() gives you incorrect results for Turkish text.