(1) that kid is not overweight and (2) it's actually OK from a medical perspective for a child to be a little overweight, as children grow in bursts, have a much better metabolism and their day is filled with plenty of exercise.
And in fact, if a kid doesn't have some meat on their bones, that's a reason for concern.
Agreed, but you're not making the argument that a potential health insurance company would (like the acne case I mentioned). And again, this is just off the top of my head. One specific case, one specific instance of "I didn't see that coming", while there may be lots and lots of other such cases.
[Edit: To make it clear, I haven't even looked at the picture previously posted, I was providing an unrelated example.]
This level of fear and worry about what an insurance company might try to argue seems too high, and not because insurance companies don't deny people for silly reasons, but because it literally isn't worth the years of fear and worry next to how little it will probably help. There are better sources of reasons to deny people, anyway, than pictures of chubby kids.
Again, this was just _one_ example of the top off my head. I could probably have come up with lots of others. My point being that we don't know how what we post today might be used in the future. Saying that it's not going to have consequences because everyone else will also do it is a very weak argument.
And in fact, if a kid doesn't have some meat on their bones, that's a reason for concern.