In the worst case, it's their NSFW algorithms identifying a nipple in the picture, with no regard for context.
If you are on facebook, you are logged into facebook, and they track every click.
Unlike the poster whose content is taken down, the reporters do not become part of public record. (I am not saying that they should.)
In the worst case, it's their NSFW algorithms identifying a nipple in the picture, with no regard for context.