I never thought to do this, but seeing that everyone has one or two of their story being taken down or clean that the story is copyright. To stop this from happening is one word "warning." If your story has adult things in it, it is best to put a warning in the story description, and for good luck, in the beginning, before they continue to read the story. Like
" Warning, this story contains sex, strong language," and so on. This way, you can keep your story up and have someone on your ass about "oh you didn't say this would be in the story." Another thing if you are doing anything gay or LGBTQ in your story, put that in the warning as well, I know it sounds mean, but trust me.
One more thing if you want 18+ to read your story, put #18andup. I hope this was helpful. This is just my experience, I'm no expert.