The canned answer is that mercedes has not developed the technology for auto body shops to bake the nano clear coat at a high enough temperature to make it set, therefore if you have something painted outside of the factory, you are SOL.

I haven't investigated this for truth, but it sounds plausible given the increase in loss of quality control from mercedes.

On a CF hood though, you are likely to only wet sand and clear coat, but I guess you could paint it, just adds weight. Anyway, clear coat is a hell of a lot easier to touch up than paint, so it shouldn't matter too too much either way.