PO files use the file format of the Gettext tools. See http://www.gnu.org/software/gettext/
For information on KDE style PO files, see http://public.planetmirror.com/pub/kde/devel/gettext-kde/
# this is another comment
#. comment extracted from the source code
magid "_: within msgid\n"
Also know as KDE style comments as they are used by KDE for message disambiguation and comments to translators. (support for this is being phased out)
#~ msgid "Blah" #~ msgstr "Bleeh"
#| msgid "previous message"
msgid "English" msgid[af] "Engels"
(This was proposed but not yet accepted in a released version of Gettext.)