Re: font-lock is broken

[Richard M. Stallman]

    If two C-g are separated by 2 seconds or more and the first is not processed
    by the time we see the second, then we can assume that Emacs is
    non-responsive and that inhibit-quit should probably be ignored.

This sounds much like the emergency escape feature.  That is disabled
on window systems because you can go to another window and kill Emacs,
if you want to do that.

We could conceivably bring it back in this modified form.
But I think it calls for some care.  Simply clearing out inhibit-quit
is likely to leave something broken.  Emacs should display a message
warning the user that that is the case.