@jon your newsletter reminded me about the very silly situation with the bus from Saarbrücken to Luxemburg. the DB may claim its compolsory reservation, but if you look on the printed timetables at Luxemburg station the CFL only say its a recommended reservation. I'm not entirely sure which one is correct, but I'm inclided to believe the CFL given they ostensibly run it, even if subcontracted to Emile Weber.
and, for thoes of us with student IDs from a Saarlandish educational institution its entirely without reservation and free of charge, I just show my student ID to the driver and walk onto whichever bus I fancy.