According to the mod:

On Sunday I was contacted by the original author with the complaint. Evidence was presented in a line-by-line comparison of the fill in question and a fic previously posted to this meme. There were multiple places where entire paragraphs appeared to have been copied and roughly edited. These instances were unique enough to call the fill into question. The original author and I discussed their options and they asked that I comment noting the similarities and asking that it be edited before posting elsewhere. The original author specifically requested to remain anon.

The comment was made and I was contacted by the filler to discus the matter. The filler was provided a link to the other fic. After reading the fic, the anon agreed that the similarities were striking and the accusation understandable, but maintained that the fic was not something they had previously read. The filler asked that apologies be passed to the original author, with assurances that it was a coincidence. Understandably with the number and type of similarities, the original author did not accept this.

Options were presented to the anon, including the choice to continue posting with only a warning. The original author expressed disinterest in having the fill removed, but the filler requested that it be deleted.

Due to the wishes of the original author I am not at liberty to present the proof as it was shown to me. Any farther information will only be released at the author's request.

Only information didn't come out in that detail initially, and everyone got all up at arms and declaired that this story couldn't possibly be plagiarised as they didn't think it was so there. Rinse and repeat sixteen times.