them people who were arguing over this topic don't know the fundamental difference between a Phd and an MD degree. Although both are 'doctorate' degrees; doctorate itself, for the purpose it's used, can or cannot be the highest degree in the field.

Phd (Doctorate of Philosophy) is a Research Doctorate Degree -- a license to teach and conduct scholarly research and is the pinnacle of the degrees one can earn in his/her field. It requires a creation of an original idea on top of the body of knowledge in the field.

MD (Doctor of Medicine) is a Professional Doctorate Degree -- gives you the license only to practice medical profession and NOT for teaching and research. It is NOT the terminal degree and hence NOT equivalent to a Phd. Other degrees, equivalent to MD, are Professional Doctorate in Engineering, PDEng (in Holland) or the Doctor of Jurisprudence(JD) in the US for that matter.

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Different countries/Universities have different names for a degree. Don't get confused or overwhelmed by the Salutation (Dr.) Even a charlatan can call himself Dr. (or Daaktar Saap) hahaha. It's just used to refer/address to the person in a society. For professional purpose, people go by appending their degree at the end of their name and which is how it should be IMO. Like

"XYZ", Phd
"ABC", MD
"123", MD, Phd

what's in a name, anyways?