how to remove keybindings?

From the wiki one of the options for dealing with keybindings is:

* Keep cfg_bindings.lua intact, and create ~/.ion3/cfg_user.lua for
your own additions. If there's a default binding you want to erase,
you can bind it to "nil" for the same effect. If cfg_bindings.lua is
left in /etc, updates will modify it to adjust to changes in function
names, or to implement new features or fix bugs.

but this doesn't seem to work with me.  Binding keys to "nil"
overrides the default bindings, but doesn't free up the binding for
applications to use.  i.e. if I add

defbindings("WMPlex", {
    kpress(META.."X", "nil"),
})

this makes ion3 eat meta-X, and my emacs no longer responds to
meta-X.  (I understand by default meta-X isn't used, but that's what
makes it easy to test...)

Any suggestions? Do I just have to disable the default bindings
entirely and replicate them in .ion3/?
--

-- 
David Roundy