Comment 2 for bug 301338

It is compiled with xfixes support.
An excerpt from the build-depends:

Source: kdebase-workspace
Section: kde
Priority: optional
Maintainer: Kubuntu Developers <email address hidden>
XSBC-Original-Maintainer: Debian Qt/KDE Maintainers <email address hidden>
Uploaders: Ana Beatriz Guerrero Lopez <email address hidden>, Sune Vuorela <email address hidden>, Fat$
Build-Depends: cdbs (>= 0.4.51), debhelper (>= 6), quilt, cmake (>= 2.6.0),
 kdelibs5-dev (>= 4:4.1.3), libphonon-dev (>= 4:4.2.0),
 libbluetooth-dev, libcaptury-dev, libdbus-1-dev, libnm-util-dev, network-manager-dev,
 libpam0g-dev, libqimageblitz-dev (>= 1:0.0.4-2), libraw1394-dev, libsensors-dev,
 libstrigiqtdbusclient-dev (>= 0.5.8-2), libusb-dev, libxkbfile-dev,
 libxcomposite-dev, libxdamage-dev, libxfixes-dev, libxklavier12-dev,
 libxrandr-dev, libxrender-dev, libxxf86misc-dev,
 libsmbclient-dev, libxcb1-dev, libxine-dev, libstreamanalyzer-dev,
 libfontconfig-dev, libglu1-mesa-dev, sip4,
 libsm-dev, libxcursor-dev, libxft-dev, libxtst-dev, libqt4-opengl-dev,
 libxinerama-dev, libxss-dev, libck-connector-dev, libplasma-dev (>= 4:4.1.3),

As you can see it's compiled with libxfixes-dev, so I guess xfixes is polling the keyboard every second?