When are genuine goods not genuine?

Until I read this story, I would have thought the answer was limited to "when they're grey-market with material variations." But apparently some car owners are buying emblems to make their genuine vehicles look like the high-end versions of the same models (or in some cases, same makes, though one suspects that's easier to detect). So we get "Mercedes eight-cylinder coupes rebadged as 12-cylinder versions, a sedan with emblems that would make it a coupe, and fake high-performance AMG or Brabus models."

This isn't the classic post-sale confusion situation, because the Mercedes is actually a Mercedes. So, does Mercedes suffer any actionable harm? If so, it can't be because of any quality concerns: Mercedes really is responsible for the quality of its 8-cylinder coupes. It can only be because of harm to the value of the exclusivity of the higher-end versions. And that's not a harm trademark has routinely taken into account independent of any other risks to the trademark owner.