That's correct, but I've never gotten false input before. If my setup gave me false input even 0.5% of the time, I wouldn't use it at all. I give myself 250 milliseconds to release the ; key to type it as normal, and that has worked fine for me, both on my laptop keyboard and on my external keyboard.
I find it very easy to use since my pinky finger sits on the ; key by default.
Did you overload the ;-key, meaning it sends ; when pressed fast, and acts as modifier when hold and pressed with other keys? Is'nt that kidna painful to use and inflicts false input occasionaly?
I too have some personal modifier-keys. I remaped Pause-key to the Right alt-key, and use for persional settings in apps. And I remapped the left Alt-key to F22, and use it for window managing and staring/raising apps.
Benefit with this is that both keys are exclusively used by me and the pause-key is also available even when my setting is not available.