I was a manager for many years, and we never disciplined anyone for discussing a write up or their compensation with other work associates.
However, we did sometimes advise an associate not to discuss a write up to protect themselves. Advise does not mean threaten or coerce, I mean some associates talk too much for their own good. They are getting disciplined and should be either embarrassed or worried, and instead they are gossiping about themselves.
Sometimes a write up might be unfair, there are always bad bosses, but most bosses don’t to write ups unless warranted, and it’s a warning and advice in what needs to change.
Reviews and write-ups 9 times out of 10 probably should not be discussed with other employees, I don’t think it benefits the person in any way. If something seems unfair I say go above their head.
Salaries, mentioned above, are usually better not discussed also, although I do agree that discussing wages and salaries is a way to check employees are being compensated fairly.
Case in point: several months after I started working as a buyer/department manager in cosmetics an employee came to me about her wage being much lower than the rest of the staff. She was being paid $8.50 an hour, and the others made between $10–14.00. That’s a lot different, she was just as productive, and had been at the company for many years. She was right, she was being underpaid. I raised her 50ยข an hour within a month of her telling me, she lliterally teared up in my office when I told her, and then we gave her a larger than usual increase at review time. She knew she was underpaid because the staff had talked amongst themselves. I had the feeling she had complained before, and nothing was done.