A single user, let alone a single employee, can certainly flag a variety of things. A user flag by itself seems unlikely to permaban a not-tiny customer, and maybe a single employee flag seems the same. However, employees are better positioned than the general public to understand the combination of small actions that will yield a big result when cranked through the mysterious nonlinear algorithm. The employee wouldn't have to understand the algorithm, because theoretically no one does. (Hello alibi!) She would just have to observe its judgments as part of her normal employment duties.