Re: frame-local variables weirdness

[Richard Stallman]

    I was asking for a way to remove a frame parameter. I don't see any
    remove-frame-parameter, and `modify-frame-parameters' can add and
    modify values, but not remove them, IIUC.

That seems like something we can add now if you really need it.
However, someone needs to check carefully that it interacts
correctly with the local binding mechanism.