all comments when made with regards to PHOTOGRAPHY.. should be just that.
not the model. to do so is considered immensely rude, whether it is xmm or not. you won't comment that a beggar looks malnourished in a street shot, or that a ballet dancer looks overly rotund, would you? the issue here is that the photographer put up the picture. if the model put up the picture then by all means, comment on her posing, comment on her looks, comment on whatever she can possibly control; but here is asking for critique on photographer skill, so things like lighting, composition, pp come into play.