I hope someone who knows better jumps in and explains why not (added not in edit), but if you want to run the car now, I say go ahead. I believe the issue with MB's and turning them the wrong direction has to do with timing the car. If you turned the engine half a turn or so and just want to run it now, I do not think there is a big deal. I have had the my cars roll backwards in gear (like 4th or 3rd on my 240D and 5th or 4th on my 190E) and never thought twice about starting it up afterwards. And never developed a reason to either. So, my personal experience says it is not a running concern, but I can see how the chain tension might change if you do this when you are lining up timing marks and the ones you can't see could be off significantly. Resetting them and then running the engine in the other direction would then lead to timing problems.
Good luck and I hope this helps! Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)