I'm on Win7. Actually I made a slight mistake on my original comment. You get "[" by pressing ALTGR+"8" not ALT+"8". Don't know if it makes a difference.
So a simple solution might be to add the following to the keypress function "if(e.altKey) return;". I've tested this locally and it works for me, but don't know if it might interfere with other keyboard layouts.
I will try applying this patch and let you know.
I'd suggest you either do "if(e.altKey)return;" or "if(e.altKey && e.ctrlKey)return;". Both work for me.
EDIT: Hm, my suggested changes work in Opera, but they break Chrome... This is driving me crazy.