With our designers and video team I constantly find running the fontbook validator and removing invalid fonts to be very helpful in improving mac performance.
I know there is a ftxvalidator app from the apple developer site here: https://developer.apple.com/fonts/ (part of the Apple Font Tool Suite, I believe), but I haven't quite figured out an ideal way to push the app out and test all fonts, removing invalid ones.
Have any of you done something to repair a system with bad fonts via self service?
