I just took another detailed look at the tires. I would say both of the rear tires seem to wear out quite evenly, when comparing the insides and the outsides of each tire respectively. However, I notice that the left rear tire is wearing out faster (and again, evenly) than the right rear one.
Note that my car is right hand drive, in case this matters.
Any help would be appreciated.
1987 W124 300E Auto right-hand drive