True, the Merc example perhaps wasn't the best. But I still agree with Annette that there *are* many such examples. Here's one. You're with a group of parents that you know to varying degrees, and one of them says her child has read the HP series 5 times and she wishes he'd read something else, but he keeps not liking things she suggests. You say, "My son really enjoyed the Philip Pullman His Dark Materials trilogy just after his HP phase." She doesn't know how old your child is, and your remark is relevant, true and useful; she won't perceive your remark as a brag. Someone else in the group, however, knows that your child is 6 and in the meantime her 6yo is struggling with The Cat in the Hat. She quite likely will - that is, her emotions will be almost the same as if you had deliberately bragged that your child was reading far better than hers. I think this kind of thing really happens. I think we do have to try to be sensitive about it - though it isn't easy - but I also think we shouldn't assume that there is fault, every time anyone feels they've been bragged at. Hurt is sometimes a side-effect, and sometimes it can't be avoided, and sometimes it shouldn't be avoided.
Indeed, if we wanted to avoid such hurt at all costs, this site shouldn't exist (or should be readable only after you've acquired a password by a complicated protocol of secret handshakes). The mere existence of our children can be perceived as a brag by people who are in an emotional place to perceive it that way - as anyone who's ever been bullied for being one of them knows only too well.