Final answer:
Markus was using social networking professionalism by refraining from posting on his public profile about his employer. This demonstrates professional behavior and protects his reputation.
Step-by-step explanation:
Markus was using social networking professionalism when he refrained from posting on his public profile about his employer. By venting to his friend privately on messenger instead of making derogatory comments about his employer publicly, Markus followed the rule of maintaining professional behavior on social media. If Markus had posted his original thoughts, he would have potentially damaged his professional reputation and jeopardized his chances of getting a job or admission to college in the future.