Thanks for the quick responses.

Brian: Nice catch, I'll add the ``obj`` shortly.

R. David: You're correct, that's exactly what happens, and what coercion means here. The language is almost the same as PyUnicode_FromEncodedObject()'s documentation, but if it's unclear I don't mind changing both. The code's comment offers another way of describing the "type modification":

/* For a Unicode subtype that's not a Unicode object, return a true Unicode object with the same data. */