If this is now your core model, then picking a new prefix makes sense to me.

The point is not so much that you’re confusing microformats parsers now that if you add microformats markup in future, you will end up wondering what u-url, u-photo or u-featured are about.

You might want to consider following a course inbetween this u- explosion and BEM where you pick constants with a bit more abstraction.

You are edging towards https://github.com/marmelab/universal.css