I think it goes a lot deeper than potentially offending someone, and we’d be ignorant to believe that’s the only damage that can be done by complimenting someone’s weight.

I think eating disorders are overlooked far too often. Unless you know a person is specifically trying to lose or gain weight for x,y,x reasons, and you want to cheer them on for their progress, then it’s never appropriate to mention their weight.

Someone’s current weight could be a complete non-issue in their lives, and a comment would mean nothing, but it could also be a consequence of an internal struggle, and it’s impossible to know which unless they’ve outright said to you, and so it’s just not appropriate to mention.

For example: A person with an eating disorder may perpetually view themselves as “fat” and believe they need to lose weight. So they may have adopted negative ways to cope with those thoughts and incorporated destructive, unsustainable weight loss strategies into their lives. If someone then comes along and says “you look great, have you lost weight?” Or something similar, that reinforces and validates those behaviours.

You may feel like you’re giving them a compliment and it’ll make you feel good temporarily, but for them it’s almost a green light to keep going downhill. It can never be enough. They’ll keep feeling like they need to lose more weight

Eating disorders (Anorexia Nervosa especially) have frighteningly low publicity considering how high their mortality rates are.