Thomas Shey
Legend
As does D&D. I mean, in any edition a MU can put on plate mail if she wants to; she just can't cast spells in it.
I consider that pretty absolute. If it just applied a failure change I think you'd have an argument. Far as that goes, I think you're wrong about OD&D; mages and thieves flat out weren't allowed to wear anything (mages) or anything but leather (thieves).