How does a manager properly correct an employee's behavior? Not like this, that's for sure.
A restaurant manager's job has a long list of tasks in the description. Making sure there's enough staff to handle customers, helping the place run smoothly, and handling any complaints or situations that might come up on a normal day of work. This means things can get awkward when an employee does something out of line, and the manager has to tell them to fix whatever problem generated the situation.
On this matter, there are many ways to correct an employee's actions. A private discussion, an email, a written warning, or, in the worst cases, a momentary suspension. I have not been to management school, but I don't think printing a giant email with an employee's picture on it and marking every mistake with a Sharpie for everyone to see is part of the crash course. I feel like there are better approaches here, especially when the infraction in question is also the responsibility of the manager.
That is exactly what this restaurant manager decided to do. An employee clashes with a customer after food took a little longer than expected. As it turns out, due to scheduling patches, for which the restaurant manager is responsible, this employee had to cover several tasks at once. That's when this super hangry man furiously claims that the food has taken too long and takes a picture of the employee without their knowledge. This picture was sent attached to a complaint email to the store. Instead of talking to the employee and clearing this mishap up, the restaurant manager decided to print the email in a giant format and place it for everyone to see. Also, she marked every visible mistake made by the employee in the picture with Sharpie. May I highlight the fact that not a single word had been exchanged with this employee at this point.