I never said it was compatible with Catmull Clark. I said it has no n-gons.

Nor is any of this relevant to the reason for the artifacts, which is that the angles are sometimes below the crease angle and sometimes above, and that failure to know what the angles are causes a cognitive dissonance. It doesn't do what some expect simply because the angles are not what you think they are.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)