Regarding custom/extra palettes

[pd]

Plus, when would it appear? There certainly wasn't an IE-style windows-message telling me that text when I added my building. It just looked horrible.

I can tell you where it appeared: In a log file.
The game DEFINITELY wrote a log file during development.

At every place those texts appear (there are plenty of them), a routine is being called. This routine has been emptied, so the game doesn't write the file anymore.
All those texts are debugging messages, like in the RMG "Seeding water" etc.
So the texts were written for debugging purposes.
Maybe they wanted to have a log file to offer a better support... (good joke, huh?)
Anyway, as we know WW was a lazy troup, and they just didn't delete the texts, but just the log file writing routine.

If I knew how to write files in assembly I could renable it...
It would also help me finding some stuff.
I should google around for that...

EDIT:
Heh, I found something, maybe it's useful.