The load position (and with that, the cascading styles order) unintentionally changed recently.
Most likely due to rMW80e5b160e098: resourceloader: Move queue formatting out of OutputPage.
It kept the exempt positions for core modules, but not for extension modules with group=user. We'll need to make the exempt logic a bit more flexible so that it also considers any other arbitrary module passed to addModuleStyles() if it has group 'user' or 'site'.