We had to change this to stricter requirements because we were getting a number of bug reports where special characters were causing glitches.

It would certainly be ideal to let you put anything you want in that category name, but unfortunately, the way the system is currently set up, that would take a HUGE amount of refactoring. Like on the scale of having to make a new category system and force everyone to convert their categories to it... (or find some way to auto-convert everyone's categories)

Eventually it would be nice to smooth this out, but right now it is just not a priority given the work-to-benefit ratio, I'm afraid D: