Comment # 1 on bug 1059438 from Tim Real

After some researching, clearly there is a problem:

I tried Yast > System > /etc/sysconfig Editor > Hardware > Keyboard
 and changed COMPOSETABLE="clear latin1.add" to COMPOSETABLE="".

This did not not turn off the behaviour.

Here is the only solution that worked:
https://forums.opensuse.org/showthread.php/450727-How-to-change-or-disable-compose-key-in-OpenSuse-11-3

It should not be this complicated to disable this incorrect 
 behaviour, nor should it be enabled by default.

It is doubtful any new user wants Ctrl keys hijacked like that.

I am not sure if this is specific to (open)SUSE,
 I read one report where a user switched to the latest
 Ubuntu and the problem was there as well.
I have an older KUbuntu and the behaviour is not there.

No KEYTABLE is in use, and now also no COMPOSETABLE. 
According to the COMPOSETABLE help, in the absence of either 
 that leaves the Kernel for default behaviour. 

Could this be a Kernel issue? Or a distro configuration issue?
If necessary could you please change this behaviour from your side.

Thanks.