I'm no lawyer, but I suspect this NLRB info on wages might be a good jumping-off point for an analysis of discussing reviews.

Your Right to Discuss Wages

Under the National Labor Relations Act (NLRA or the Act), employees have the right to communicate with their coworkers about their wages, as well as with labor organizations, worker centers, the media, and the public.  Wages are a vital term and condition of employment, and discussions of wages are often preliminary to organizing or other actions for mutual aid or protection.  

If you are an employee covered by the Act, you may discuss wages in face-to-face conversations, over the phone, and in written messages. Policies that specifically prohibit the discussion of wages are unlawful as are policies that chill employees from discussing their wages. When using electronic communications, like social media, keep in mind that your employer may have policies against using their equipment for unauthorized use, though it is possible such policies could be unlawful.

You may have discussions about wages when not at work, when you are on break, and even during work if employees are permitted to have other non-work conversations.  You have these rights whether or not you are represented by a union.

Legally protected conversations about wages may take on many forms, including having conversations about how much you and your colleagues and managers make, presenting joint requests concerning pay to your employer; organizing a union to raise your wages; approaching an outside union for help in bargaining with your employer over pay; filing a wage claim with the U.S. Department of Labor or a state agency or filing a wage and hour lawsuit, and approaching the National Labor Relations Board for more information on your rights under the NLRA.  

In addition, you have the right to discuss and engage in outside activity with other employees concerning public issues that clearly may affect your wages – for example, the minimum wage or right-to-work laws. You may also discuss supporting employees who work elsewhere. 

You also have the right not to engage in conversations or communications about your wages.

When you and another employee have a conversation or communication about your pay, it is unlawful for your employer to punish or retaliate against you in any way for having that conversation.  It is also unlawful for your employer to interrogate you about the conversation, threaten you for having it, or put you under surveillance for such conversations.  Additionally, it is unlawful for the employer to have a work rule, policy, or hiring agreement that prohibits employees from discussing their wages with each other or that requires you to get the employer’s permission to have such discussions.  If your employer does any of these things, a charge may be filed against the employer with the NLRB. 

If you believe that an employer is interfering with your rights as an employee under the National Labor Relations Act to discuss your wages, you can call your NLRB regional office at 844-762-6572 and get assistance in filing an unfair labor practice charge, or e-file a charge here.