Cannot use shortcuts with "Meta" (aka Super) key

[Enrico]

In Kubuntu 15.04, both with and without the backports ppa, one cannot successfully configure shortcuts involving the "Meta" key. So if one sets "Meta+q" as the quit shortcut in the kcm, applications don't react and print the q (I've tested konsole, kate, konversation and a few other).
This is reported as bug #1449816, with regard to konsole, but in fact applies to other applications in KDE (I haven't tested all of them).

This cannot be reproduced in Fedora 22, openSuse Tumbleweed or Kubuntu 15.10.
I post this bug under kubuntu-meta (out of ignorance, mostly).