Sorry, I did not understand your idea in the gnome bugzilla. Now, let's talk about it.

If I understand you right, you want backspace to behave like ctrl-backpace. What you can try is set modifier_map Control to Backspace. If the apps just use the modifier, it might be enough.

In symbols/us file, 'colemak' section, add

modifier_map Control { BackSpace };

at the end. Then reload xkb configuration.

That sounds like exactly what I want! When I get home and have some
time I'll have to try that.  Thanks a ton!

Ok, I added that line to the end of the colemak section of
/usr/share/X11/xkb/symbols/us

I don't know how to reload the xkb configuration, so I guess I'll just
try logging out and in, restarting, etc.

That didn't work, and I can't find any relevant man pages or sites via
google, no response on #xorg..

How do I reload the xkb configuration?

Well, debugging xkb sometimes is tricky, and there is not much docs. See http://freedesktop.org/wiki/Software/XKeyboardConfig, the Links section.

Restarting X is usually enough.

Would you attach the result of "xkbcomp :0 -xkb out.xkb"?

ethan@home:~$ xkbcomp :0 -xkb out.xkb
Warning:          Could not load keyboard geometry for :0
                  BadAlloc (insufficient resources for operation)
                  Resulting keymap file will not describe geometry

> Warning:          Could not load keyboard geometry for :0
>                   BadAlloc (insufficient resources for operation)
>                   Resulting keymap file will not describe geometry
First of all, it is a warning, not a error. Second, it shows there something wrong with your xkb (probably, in X server). How do you start X? Do you use gdm autologin or smth? Try to do just 'setxkbmap', it might refresh your xkb configuration.
You should still get out.xkb with necessary details. Please attach it here.

Created attachment 25375 [details]
out.xkb

Evidently you can't attach things to bugs in bugzilla via email.  Learn something new every day.

Well, it's attached now, sorry about that.

I have confirmed that the qwerty backspace key is acting as both ctrl
and backspace.. so if I hold backspace (repeat is off), and hit 't',
it makes a new tab..  if I hit backspace and then (capslock)backspace,
it deletes the last word I typed.
I switched ? and /, so I know I'm applying the latest 'us' layout file here.

Now that I know kind of what's going on, I should be getting closer to
what I need..

Well, I hate moving my fingers to shift, when I've got two thumbs, so
after I figure this one out, I want my spacebar to act as a shift
modifier while held down, but if let up before another keystroke,
produce a space.  Eventually, hopefully, I'll get a keyboard with a
split spacebar so I can just remap each key how I will, but on a
laptop, that's not likely.  I think I'll try locking the shift
modifier to the space key and just see how that goes.

> Now that I know kind of what's going on, I should be getting closer to
> what I need..
Well, it was clear from out.xkb that your configuration was reloaded. But that did not actually work - it seems XKB is checking the state (of the Control modifier) before it changes it. Most probably, it is impossible to change, at least ATM I cannot think of any way... Let me look a bit more.

What you also can try:

key <BKSP> { [BackSpace], actions[Group1] = [SetMods(modifiers=Control)] };

But I am not sure that the action will be performed before the modifiers check...

no reply for a year