The mutual non-disparagement contract is not all that mutual. As an employee you are prevented from talking bad about the company, so you will say nothing about them. However, if you are looking for a new job, your new employer may call your old employer to check up on you. If there is a mutual non-disparagement contract at play, they will be passed to the corporate console who will tell them that so and so employee did work for the company from date to date, but they can not discuss the matter any further. For all employees this is a huge red flag. And the best thing, when asked about it, the employee would not be able to explain the situation because of the same contract.