It seems the issue has two roots (at least for Polish translation):
1. upstream translation - similiar issue is also visible in other distributions than Ubuntu.
Solution is fixing translation due to the guideline at upstream .po file:
#. For best results (df header/column alignment), ensure that
#. your translation has the same length as the original.
#. Also, each column name translation should end at the same
#. column as the corresponding original.
The guidline is present in more recent coreutils package than 7.4 (that on Ubuntu 10.04), I don't know exactly at what version it was added. The above is taken from coreutils 8.8 po/pl.po you can find at upstream site).
2. Ubuntu translation - the df output is even more shifted than the original one
Solution/workaround is the same as above.
For Polish translation there is a patch provided within bug report that has been marked as duplicate of this bug:
link to the patch file: