i'm a writer irl (can't say who because my agent would rightfully put me into a blender and press the button if i go and out myself as "balrogballs") and honestly the funniest and most humiliating incident of my life was the time my finished manuscript triggered a plagiarism flag with the publisher for two lines of prose in my literary fiction novel...
.... which was word for word similar to a paragraph in a certain explicit work on FFN starring elrond and his batsman from the hobbit films, aka that one elf that looked like he ate panic attacks for breakfast (i forget his name but it's Figwit II) where the lord of imladris bends said twink over his writing desk and gives him the battering ram treatment.
and if you think i had to sit in front of one if the biggest publishing companies in the world and admit that it was, in fact, me who wrote the fic where the lord of imladris bends said twink over his writing desk and gives him the battering ram treatment in order to avoid being wrongly flagged for plagiarism, you would be absolutely correct.
(yes they published the book)