In fact, for years, I tended to point out the not so flattering aspects of people. This habit probably came from my mother, who often commented negatively on people and places. I can hear myself saying, on more than one occasion, "You've put on weight," or "You should never wear orange." In fact, someone once said to me - If your best friend won't tell you, Carol will."
Somehow, I changed. Maybe once I was out of the negative environment of my home and spending more time with positive people, I began to think more positively. I didn't always compliment, but, at least, I didn't say, "Too bad about your fat ankles."
The more I saw the good things in people, the more I realized that mentioning these assets was uplifting. I didn't seek to flatter. I sought to "make some one's day" or at least an hour or two of it. I know, I always felt much better, when someone said, for example, "I really like your hair like that" or "you have such great kids." I know it's not flattery. No one has anything to gain, by complimenting me, unduly. I think that they have just made a habit of saying something positive, often.
This positivity, can I say that, might be a little like "showing something to advantage." I know this is one of the meanings of flattery. However, I can't see anything wrong or insincere with wearing black, for example, if you are overweight, because it is a slimming colour. Self help books, often say, show off your good points - put on make-up, stand tall, smile. I think flattering yourself, is a way of improving yourself and in my books, that's just fine.
The pictures? Fishing for compliments - sorry I couldn't resist!!