What is the usecase for "keep a standard shortcut while adding a non-standard one"? So far I don't see a real advantage but a corner-case, compared to a more complex UI for everybody.

I won't defend my second example (my use case is that sometimes I define a non-standard shortcut for my own use, but that confuses other users who just want to do something quick, like use a web browser, and not switch to another account).

The first example is widely sought, however:

http://askubuntu.com/questions/88215/secondary-keyboard-shortcuts-in-gnome
http://unix.stackexchange.com/questions/119021/dual-keyboard-shortcuts-in-gnome

This needn't make the user interface more complex for the normal case of changing a shortcut, as it can be done in custom bindings: make it possible to have a desktop action instead of a command as the result of a keystroke.

(In reply to comment #2)
> I define a non-standard shortcut for my own use, but that confuses other users

Not if other users don't use your personal user account with your settings, but a separate account on a multi-user system.

I said specifically: "other users who just want to do something quick, like use a web browser, and not switch to another account". But it was a bad example in the first place. Please ignore it and concentrate on the first use case I offered, namely, multiple key shortcuts for media actions.

Thanks for taking the time to report this.
This particular bug has already been reported into our bug tracking system, but please feel free to report any further bugs you find.

*** This bug has been marked as a duplicate of bug 373934 ***