If any admin privilege was used to get that information, it should be illegal posting that information public just for the sake of it.
If the conclusion that someone is an alt of a certain player was made via regular analyzing (part C of Chewett's post for instance), then it is quite 'legal', although rude and frowned upon in most of cases, it depends on the circumstances. (perhaps a certain abuse or deception was prevented, and in that case posting would be socially very acceptable. Very much frowned upon if a player wanted to try out a new role and perspective on things, and you just ruined it for the player just because you can)
Anyhows, if admins privileges were not used, then at the end, as it was said already, the alt has a certain dose of blame to get as well for not managing to keep his identity secret (meaning, new role was not conducted that well), and exposing the identity is, kind of, free game.
The thing with Dst, in recent events, is that I am completely ignorant of the fact is she getting those conclusions based on that legitimate analyzing, or via some admin tools, IP checkers and such.
Perhaps she would be willing to share that with us? To add one more thing:
Let's take Dst as an example. A player develops a conflict with Dst, then makes an alt. The alt keeps this hostile attitude towards Dst - it means that the traces of your main account persona were transfered to your alt, and that the whole concept of new role/perception falls to the water, because ideally the alt should develop a conflict with Dst from scratch, not receive it as a legacy of the previous account.
In that case, Dst's retaliation of posting the alt information is 'fair' (again, if no admin tools were used).
Dst didn't leave the impression that such was the case with Poe and Magistra when posting their information, and it is unknown whether certain admin privileges were used, so do not apply this example to events that took place.