Sorry, Martin, but what I´m trying to achieve is irrelevant. I need to do it, and asked how. The kind people on this list told me the best way they knew. In any case, what I´m trying to do is to do a clean install of KDE5 on a long running sid system. On KDE4 it was easy, I just had to remove the .kde folder, for example.
Yes, that´s what I thought too, Brad. purge would not touch my home config files. Thanks.
So I´ll remove all packages by hand and the config files one by one - it seems that is the only way.
Thanks everyone for the input.