The solution to privacy issues is not to make everyone anonymous. (Nobody ever actually puts it that way, but a lot of people suggest solutions that basically amount to the same thing.) Under-identification is as much of a problem as over-identification. Reputation and social pressure also prevent a lot of bad behavior. For that to happen, we still need people's identity to have some continuity ... and that's where pseudonyms come in. Go look at the examples in the OP. Practically all of them involve some kind of "leakage" from one part of a person's life to another. This is the same problem that has existed since before computers, with people having safe persistent identities within one community until they're "outed" to the broader one. If people had more control over the different parts of their identity, to connect them or not as they see fit, these things couldn't happen. Better technical and social support for pseudonyms might not be a panacea, but it would certainly go a long way.
Hard problem for sure, and curious to hear how others think about the issue of minimizing trolling while maximizing privacy.