Comment # 1 on bug 919673 from Bernhard Wiedemann

I agree that a Linux system should just keep working.

a) would be interesting, why there is so much data in /tmp/kde*

b) in principle you could place /tmp , /var/tmp , /var/log etc 
on a separate partition, but it was not the default
and even then certain programs could fail because they need space there.

Not sure if it is different with btrfs subvolumes these days.