Don't know, but I suspect it is to prevent overly fast action on the system to prevent "bouncing" up and down. Strange things happen when the German manual get translated into English -- usually British English, at that. Damper = shock absorber = slows things down, absorbs vibration/ocsillation. There is, for example, a damper in the old sidedraft carb on the 115s filled with transmission fluid that prevents the mixture control needle from "buzzing" in the orifice (it was a variable venturi carb, pretty fancy in theory, a pain in the ass in practice).
I would assume that if it is bad, the autolevel won't work properly.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!