After some hacking I have got a nice requested feature for the folder view containment. Mime type filter support. I took some screenshots so you can have a look yourself.
The filter is set to “show all file type folder that starts with kde”.
This time the pattern filter is null, so the folder view shows all folders on my home directory.
I set a “hide all folders on my home directory”.
You will see this very soon on trunk, 4.2.