I do think Michael had major insecurities about his appearance but that doesn't necessarily mean he had a disorder. Michael was always handsome to me but I can't say that his insecurities were irrational (as BDD is). He was a teen idol with severe acne on his face. He had a growth spurt when he went through puberty although the public were still expecting cute little Michael. Remember that story Michael told of a woman who approached him and his brothers and asked "where's little Michael?" and Michael said "I'm Michael" and the woman just said "Eww!"? That kind of experience would affect anyone's self-confidence. Then you had his father and his cousins teasing him about his nose and given how ubiquitous cosmetic surgery is in Hollywood, it's not surprising that he had it changed when he could. You could say he took it too far but perhaps Michael liked it that way? His nose always reminded me of that of Disney characters, with the tip pointed slightly upwards. Then he was diagnosed with lupus and vitiligo, which are both disfiguring conditions that cause depigmentation, rashes, hair loss, lesions, scarring, etc. He suffered third degree burns on his scalp which left a bald spot. The medication he had to take for his auto-immune diseases caused bloating ('moon face') and nail discoloration. All the while, the media and the public relentlessly mocked his appearance, plastering his most unflattering pictures all of the news, magnifying every perceived flaw, even going so far as to suggest his changing appearance meant he hated his race.
Yet despite all of this, Michael took great pride in how he presented himself. He dressed like royalty, especially in public. He comissioned paintings and photoshoots of himself for artistic purposes and hung them in the most public places of his house. His three best-selling albums Off The Wall, Thriller and Bad have a cover that only features him. He had a freaking statue of himself in many major cities around the world as promotion for HIStory.
So to compare the genuine insecurities he had about his appearance to a serious psychological disorder like body dismorphia does not seem accurate to me. His insecurities never prevented him from having a fulfilling (and very public) career.