OK, I need to update this one.
apt-get did do the job right, it's that I've forgotten that Akonadi is an extensible
cross-desktop Personal Information Management (PIM) storage service (though it comes from KDE camp), so it wasn't removed automagically. I had SMPlayer installed too, which uses some things like and from KDE I believe, so search for KDE in Synaptic, mark everything what you don't want for complete removal > Done. No more KDE in /usr/bin/ (in one way or another).
Really, apt-get is a piece of work.
Synaptic too!