"Oh dear, I've often told people they look well, when what I meant by it was: 'you look well'.
Healthy, glowing, rested, good.
I had no idea they were taking it has a back-handed euphemism."
This! I'm mortified to think I've been merrily wandering around hurting feelings when I literally meant what Dowager said. 
As someone whose doctor previously (accurately) described them as "enormous", but who now veers between healthy and healthy+ (now there's a euphemism I like
)...there's a world of difference in how people speak to you and treat you generally when you're fat, even when they're being kind. Whether it's meant that way or not, "you've got a pretty face" sounds as if it's saying "the rest of you isn't pretty".
Flipping it round, once our manager said to his PA (meaning it as a high compliment), from the neck down you're a very beautiful woman. 