Hi, which demo were you trying? and what version of Opera and FF?
FWIW, Opera has a preference to disable single key hotkeys, but that still didn't help in the platform game, because pressing comma in Opera activates the search-as-you-type.
Maybe you need a way to let people remap. But it would be worth mentioning at the outset that Opera users will run into these issues.
Opera info: Version 10.10
Build 1893
Platform Win32
System Windows XP
Java Sun Java Runtime Environment version 1.6
XHTML+Voice Plug-in not loaded