Many people have sued Sean Combs (P. Diddy) for alleged sexual assault in federal court in Manhattan (S.D.N.Y.); many of those have sued pseudonymously. So far:
[1.] Some judges have allowed the cases to go forward under a pseudonym (Doe v. Combs) until Combs' lawyers enter an appearance and have an opportunity to oppose pseudonymity. The orders (see, e.g., here, here, here, and here) have mostly been short, but have offered at least some reasoning; here's one from Judge Lewis Liman:
In determining whether a Plaintiff may proceed anonymously, "the plaintiff's interest in anonymity must be balanced against both the public interest in disclosure and any prejudice to the defendant." A court should consider factors including whether the litigation involves matters that are "highly sensitive and of a personal nature," "whether identification poses a risk of retaliatory physical or mental harm," whether the defendant is prejudiced, whether any such prejudice "differs at any particular stage of the litigation," whether any such prejudice "can be mitigated by the district court," and the public interest.
Plaintiff has made a preliminary showing sufficient to permit the filing of the complaint and the issuance of a summons. The nature of Plaintiff's sexual assault allegations is highly personal, and Plaintiff states that Defendant Sean Combs threatened her with violence if she spoke of the alleged assault. Given that Defendant is a public figure, revelation of Plaintiff's identity may also lead to significant, potentially harmful attention from media and the public. However, Defendants have a right to be heard, the Court must take the interests of the public into account, and "the balance between a party's need for anonymity and the interests weighing in favor of open judicial proceedings may change as the litigation progresses." Therefore, Plaintiff shall file a renewed motion to continue to proceed anonymously within 30 days after service of the complaint. In the absence of a timely filed motion, the Court shall order the name of the Plaintiff be disclosed.