There is a distinction between plagiarism (the unacknowledged use of someone else’s words claimed as one’s own), fanfiction (the acknowledged or obvious borrowing of story elements to tell a new story in the fanfiction writer’s words), and quotation (the acknowledged or obvious use of small excerpts of another’s work).
By “obvious” we mean that even if a fan writer didn’t put a disclaimer on their story, readers know that they did not invent Wonder Woman or Voldemort, or the phrase “Use the Force, Luke.”
Plagiarism is deceitful and prevents the original author from receiving credit for their own original work. Fanfiction and quotation are important fair uses which acknowledge the original author and their work. The OTW does not support plagiarism; we do support fanfiction and quotation.