Thia Halmades said:
Spatzi has an excellent point; just because you aren't sociable doesn't mean you aren't a virtuoso; one doesn't necessarily follow the other.
To be fair, I can see the counterpoint, and so IMC we do penalize Perform. No matter how fantastic your playing is, if you're an ugly monster, the audience is going to be distracted, and what the Perform check result represents is the overall effectiveness of the performance. In the ages before recordings were possible, appearance mattered; it wasn't just used to distract from an inadequate performance, it was usually PART of the performance. If the audience is uncomfortable around you, it's going to detract from the experience, even if your music is fantastic.
But does that apply to every type of Perform check? Epic storytelling (or dirty jokes) never really relied on that sort of flashy appearance. There's always a use in drama for the ugly, mean-looking guy (the same logic that gives a bonus to Intimidation could be used here). When playing an instrument, you could probably get around the appearance issue depending on the lighting, etc.
For balance reasons, I include Perform on the list of skills to be penalized. However, there's a caveat; any of these "social interaction" skill penalties should be able to be removed depending on circumstance. First, there's the Cyrano effect: if my Half-Ogre writes a beautiful ballad, and someone else plays it exactly as written, whose Perform check is used? (Answer: both, really, but neither would be penalized by my appearance.) Then, familiarity; if I'm Bluffing (or telling dirty jokes to) my friends, who clearly aren't upset by my appearance, should I still get that -2 penalty? (Flip side: if I Intimidate my friends, who KNOW I'm not really a psychotic baby-eating beast, should I still get a +4 bonus?)
And again, on UMD checks; why wouldn't you be able to Use Magic Items? If they're intelligent items I can see them forming an opinion of you, but my pen doesn't have a strong feeling about me, neither would a wand.
The more I think about this one, the more I think UMD shouldn't be CHA-related. There's just no reason. Why should the ability to imitate a Wizard depend on personality and appearance? "Force of will" is all well and good, but it's never been made clear exactly what the mechanism involved is. If anything, I feel it should be a WIS-based skill; I'd personally prefer having no linked stat, but that'd require reassessment of all the DCs since the average bonus would be lower.