One of my favorite SF short stories was in Analog in the 80s (maybe?). It was a series of query letters from an SF writer, and responses in which the editor accuses the writer of plagiarizing stories that were published in the 30s. As the story goes on, you realize that in fact the stories are being stolen by the inventor of a time machine. The editor doesn’t believe him, until the writer bundles up the shared correspondence into a story—which they discover has already been published.