It is enforced on all airlines as the poster says, nevertheless it is an abusive clause at least in Europe, and LH has been fined because of that.
Now the very possible outcome is to be denied boarding, made to buy a new ticket (at much higher price) and never see your money back.
Let's make an end to stupid and schizofrenic pricing structures and strategies!!!
I wonder if anybody would do a test case risking little money on special fares within Europe just for the purpose of suing the airline and make a doctrine out of it.
see reference to case in Germany on the ECTAA website:
http://www.ectaa.org/Home/Publicatio...S/Default.aspx