It might be that this should be discussed as a proposal of UI Events, though. However, I think this is very useful for web applications which implement their own shortcut keys.

Proper modifier key which should be used for shortcut key depends on platforms or user settings on UNIX like OS. Especially, it's impossible web apps to know proper modifier key(s) for shortcut key on UNIX like OS (I guess that most users of Linux expects ctrlKey, but somebody especially who uses Sun keyboard or Mac keyboard might expect metaKey).

accelKey should be true if modifier key which is expected as shortcut modifier key by the user. E.g., it's alias of ctrlKey on Windows, it's alias of metaKey on Mac.

If this is defined by D3E, web apps don't need to check platforms and guess proper modifier key for shortcut themselves.