The rolling back I saw was on flat pavement. No hill. Guy was being an asshole.
If car was rolling, there was an incline. I've driven a manual trans for 50 years. They don't roll back on a flat w/o a push... That said, I can't imagine why anyone would WANT to roll back into someone. The way bumpers are constructed, he's just as apt to get a dent as you are, I'd think. Hills - that's a different story, lol. IL, I think you made a good call with having a Hermann-friendly zippy car!