User
I recently had my exit interview with the HR manager of the company I work for. They started the interview by telling me anything I say is "in confidence" and "will not leave these four walls". Since then it transpires they've shared the things I said with my head of department, and they've been discussed with my line manager.
Is this a common scenario, and was I wrong to trust them?
User
Yes, it is actually very common. The only way that your exit interview will make an impact on the company is if what you say is shared with your boss and the higher-ups in the company. It's also very hard to anonymize what you say, as your boss will know who it's coming from the moment they hear "this is coming from the exit interview" from the HR person.
That said, if you started ranting or cursing out your boss to the HR rep, your boss will hear about that too, and probably just think that you're a disgruntled employee who was causing problems more than wanting to solve problems.