A female instructor has had conflict with a much younger male co-instructor and has complained to her chair and associate chair about what she experienced as sexist and other difficult behavior. When the new schedule for the following year again has her paired with the same co-instructor, she asks for a different assignment. The entire message is very short, basically, "Oh, please don't pair me again with X. He's an uncooperative young male. You said you'd pair me with Y." Y is also a much younger male, only slightly older than X. She's worked with Y in the past and it's clear she likes him.
Unfortunately, instead of replying only to the associate chair, she accidentally reply-alls to the entire department. She apologizes to the department a few minutes later for copying everyone on what was intended as "a private response". In a private email to the associate chair a few hours later, she makes clear she's complaining about gender bias, that she believes her co-instructor disrespects her in part because she's a woman. (Complaining about gender bias is a protected activity in the US, meaning, e.g., it can't be used as a reason for an "adverse employment action" like denying promotion.)
Most recipients of the reply-all did not know about the previous complaints. The chair and associate chair both knew about the complaints. Only the associate chair also knew about the later email.
A few hours later, the promotion committee begins discussion of her major review, leading up to a vote on her contract and possible promotion. The unfortunate reply-all is discussed and some of the members express shock. Only the chair and associate chair are aware of the previous complaints and neither reveals that information. To the contrary, the chair uses it in his words as an "opening" to argue she was involved in lots of conflict and that questions of who "instigated" the disagreements should "explicitly" be set aside, remarking, "We're really not trying to adjudicate any of the disagreements." So, different people knew different things. In a split vote, the review fails. (Months later, everything becomes more widely known.)
Was it appropriate to discuss the reply-all and did that taint the process? To answer, you may need to decide if it was a protected complaint about a gender bias or perhaps something else, and whether the chair and/or associate chair should have disclosed the previous complaints or the follow-up email declaring it to be a complaint about gender bias.