How to disable Qt accessibility in 12.04?
Solution 1:
The package maintainer at KDE level provided a hint.
If everything fails, check which package installs /usr/lib/x86_64-linux-gnu/qt4/plugins/accessiblebridge/libqspiaccessiblebridge.so and try to remove it. If you cannot, because of dependencies, you can manually move the file away as root, and restart the desktop. This should remove support for Qt accessibility.
On Ubuntu 12.04 that boils down to sudo dpkg --purge qt-at-spi
which effectively disables Qt accessibility.
This is a bit brute force (for example, it does not allow to enable accessibility for some users only), but it does answer the question with an effective solution, right ?
Solution 2:
I found an answer. Make kaccessibleapp not-executable. That will prevent it from starting back up.
sudo chmod a-x /usr/lib/kde4/libexec/kaccessibleapp