Hi, so yesterday's change in layout baffled me (I've now read that the larger text is a bug which will be fixed). In trying to fix it myself, I wound up setting my preferences back to the default, which was a mistake since it just undid several useful settings.
Most of them I've managed to fix, except an important one: disabling the category module. I've selected source as my preferred editor, clicked "Disable Category module," and nothing seems to work. I've widened the source, which causes the module to disappear when editing, yes... but it also fails to show existing category code (and the module is still present on all actual articles).
I work on Muppet Wiki, where we edit categories manually (since it's the best way to sort, to make sure article names are alphabetized or "The" and "A" articles not factored, and so on). I've tried logging in and out, clearing cookies, etc.
If I need to send this to someone else, let me know. In the meantime, here's some screengrabs and details (I'm using IE11, Windows 7, 1600x900 resolution). Right now, the only fix I've found that works is just switching back to Monobook, which has its own drawbacks.