You have seen it used many times, but it often passes by without notice. It’s entirely possible that you had an English teacher who said it should never be done. You may have never contemplated using the second person perspective, the most direct and directed form. But you have seen it used all over the internet as one of the most immediate and direct ways of speaking to someone.
You can use it as an accusation or from inside someone’s head. Through its many uses and distinct flavors, you will find that nothing suits the internet quite like second person.