Your other question went unanswered...the damper keeps the belt in tension, yet allows for some movement due to engine vibration without allowing so much slack that the belt comes loose.
Never seen such a system on other makes, and it does appear to be an odd design, but it works.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car