IF the comments--1) Were discriminatory against a protected category (e.g. race, religion, age over 40, sex, disability) or2) Were defamatory, in the sense of being untrue statements of fact that harmed the employee's reputation or made others not want to work/do business with him (note: opinions are NOT defamation, so it's "ok" for a manager to say, "Joe was a jerk" or "Joe's whinning about unimportant issues."If the above is the case, the employee may have a legal claim against the company or the manager. Or (3) if the employee had a firm disciplinary or grievance policy, as reflected in an individual contract, a  union agreement, or an employee handbook that did not have  ANY of the usual caveats or limitions (e.g. did not say "policies may be changed at will," or "this does not create a contract"), then the employee may be able force the company to honor the terms of its own agreements.In the absence of the above, there is probably very little recourse for the employee, however,