This is the lengths of despicableness that people will go to.
Multiple persons have an issue with their manager, who shall be refered to as person C.
So Person A, messages their friend, person B about person C. There's some back and forth (as there is in most conversations) and person A assuming this was a confidential conversation between 2 friends thought nothing of it.
However, (and here comes the point), person B decides to print off the conversation, show it to person C, who promptly gets Person A fired. With immediate effect.
Now really, who the flaming shit does that? To a supposed friend no less...