If you are talking posts made on PPRuNe, this site is "published" in the State of California where the legal system provides for:
A Doe subpoena is a subpoena that seeks the identity of an unknown defendant to a lawsuit. Most jurisdictions permit a plaintiff who does not yet know a defendant's identity to file suit against John Doe and then use the tools of the discovery process to seek the defendant's true name. A Doe subpoena is often served on an online service provider or ISP for the purpose of identifying the author of an anonymous post.
And:
A strategic lawsuit against public participation (SLAPP) is a lawsuit that is intended to censor, intimidate, and silence critics by burdening them with the cost of a legal defense until they abandon their criticism or opposition.
The typical SLAPP plaintiff does not normally expect to win the lawsuit. The plaintiff's goals are accomplished if the defendant succumbs to fear, intimidation, mounting legal costs or simple exhaustion and abandons the criticism. A SLAPP may also intimidate others from participating in the debate. A SLAPP is often preceded by a legal threat.
Forget about fairness and the rules of libel and defamation. It is not necessary for a plaintiff to prove libel or defamation in order to obtain the IP address and any other information held by the publisher of a web site such as PPRuNe. In general, there is no defence to a SLAPP Subpoena.
PPRuNe has received a number of SLAPP Subpoenas in recent times. One airline in particular does not wish to be discussed in what it perceives are derogatory terms. A SLAPP Subpoena may request and obtain the identities of many users who have posted on PPRuNe (I think one SLAPP Subpoena sought details on 40 plus posts) and many of those posts may be totally innocent and mundane.
Be very careful before you press the "Submit Reply" button!
And don't admonish Mods for deleting posts and threads when Mods are probably aware of other considerations and delete posts or threads in order to protect you, our registered users.