The difference is not in the information, but in the intention.
I get confused myself sometimes because I learned that bragging was distasteful and while that is essentially true, I didn't learn the difference between bragging and sharing so I lumped them together. I learned to protect my good news, because I didn't want to risk that it wouldn't be celebrated, that somehow I would be judged or worst of all, that my good news would make someone else feel bad.
Out with a friend and hearing how great everything is, while knowing in my gut that a massive coverup is going on, that is 'the bragging effect'. There is a smell of the inauthentic that gives away the pain underneath the surface.
There is also the phenomenon of bonding over negativity, where darkness feeds on darkness and relationships bloom in gossip and complaints. I have experienced that too and while it can be sickly satisfying for a moment, it's like drinking too much and leaves you with a nasty hangover.
I don't want to sit with friends and negatively bond, I also don't want to hear (or say) how amazing everything is if that's not the case.
I think it boils down to authenticity and I know now that sharing the bad AND the good - the TRUTH, brings more light into the world, and what could be better than that?