Re: `buffer-list' and the frame-parameter `buffer-predicate'

[Richard Stallman]

    The whole idea behind this is to get the buffers sorted. It is like
    keeping my stuff sorted in different drawers instead of keeping it in
    one single box in the middle of my room.

Now I understand.  The idea of limiting which buffers you can switch
to is not the issue, I think.  What you want to do is limit that
buffers are included in lists that are shown or offered to you.

It should be easy to do as a customization that by writing
replacements for the buffer menu commands, for list-buffers, and for
switch-to-buffer (supplying a different list for completion, perhaps).
I suggest you give these commands new names and bind them to keys as
you see fit.  That is cleaner than redefiniting the standard
functions.

As for making this a feature in Emacs, the question is whether people
can develop simple and easy-to-use ways of specifying which buffers
to list for each frame.  I think that is the crucial issue.
If those methods are simple and don't require users to remember a lot,
they could be widely used.  Otherwise they won't be used much, so it
is not worth the trouble of adding them.