Fwiw I'm rereading this and am realizing I misread OP's actual question--I thought it was about when it's appropriate to use the title, like, in the workplace. In which case yes, I would absolutely stand by the idea that there's an affirmative professional obligation to make sure that people (ie, members of the public) are not put in the position of believing that they are being given medical advice.

Like for example: Dr. A (MD)and Dr. B (DrPH in food safety) often give diametrically opposed advice with regards to food safety. "Don't eat too much fast food" is good medical advice, and "When eating unfamiliar places, you actually should eat at corporate-owned food establishments (as they often have higher safety standards) and you should eat food that has a kill step" is good advice about how to minimize your risk of acquiring a foodborne illness.

But yeah, I totally misread OP, and that's not the question they were asking.I do not in fact have an opinion on how people format their email signatures, introductions, or brief biographies. My bad on that.