So, I wasn't totally happy with the standard BE layout, a few keys were dead keys when I didn't want them to be, but the variant without dead keys went too far the other way.

To try and fix that, I edited the /usr/share/X11/xkb/symbols/be file and I changed the standard layout the way I wanted.

I know this isn't a very clean approach, but I'd just like to reiterate that I edited the very same layout I was using at the time. You'll get why I'm emphasizing that soon.

Now, those modifications did not take effect right away. Understandable.

But they didn't even show up after I rebooted. If I use the tool to change layouts, it works! But if I check 'Use system default', it just doesn't.

Puzzled by this, I googled and found some information about dpkg-reconfigure keyboard-configuration

So I executed that and lo and behold, it did indeed change the system default keymap. Apparently, that must be a copy or something that's stored somewhere.

However, I now want to make another change to my keymap. So I went and did the same thing again: edited the symbols file, executed the dpkg-reconfigure. Think it works now?

Nope.

My system default is still the old edited version and no amount of reconfiguring changes anything. Yes, using the GUI tool I can use my new edited version, but I can't seem to install that as system default. Why? Where is that system default keymap? Some google results say that it's compiled into the kernel, but the first successful reconfigure did not require recompilation of anything. But why did the reconfigure work once, but not twice???

This is the sort of black magic I expect from Windows...

Can anyone shed some light on this?