I'm sure that young people don't see any difference between saying something defamatory and putting it out on social media. One is slander and rarely actionable without proof of financial loss; an exception at common law is impugning a woman's chastity, which says a lot about bygone times; the other is libel and actionable without financial loss. But most youngsters are safe, because they are not worth suing. It is still possible for people to get injunctions forbidding the world and his wife from referring to some embarrassing fact about them, but these have fallen into disfavour and are hardly worth an application.
People are more in danger of being in contempt of court. They don't appreciate what that covers, nor that it is putting words into text,rather than just gossiping with friends, that gets them into trouble because it's then that the harm is done.