The thing is, you aren’t the strata manager’s client, the Owners Corporation is. It is sometimes a fuzzy distinction but the strata manager is contracted to and acts on behalf of the OC. Any communications he receives, he receives in that capacity, i.e. as agent for the OC.
As I said previously, if you want a communication with the manager (or anyone else) to remain confidential, then you should clearly indicate that, for example by heading an email “confidential” and in the text stating that it is not to be circulated to anyone else. There is no such thing as “automatic confidentiality”, and even if you take the steps I mention you can’t guarantee that confidentiality will be maintained unless the other party agrees to it.
In terms of other information the manager might have, it depends on what it is, for example personal information is covered by legislation such as the Privacy Act and the manager is bound by that. A Code of Conduct is not really worth much of itself, if the manager is actually bound by one.
The manager’s use of the word “entitled” is questionable, that word is bandied about a bit too much these days. I wouldn’t say he was entitled, but he hasn’t done anything wrong in the strictest sense.
However – he sounds like a prat, the real issue is that you have a complaint about him, he didn’t like it, so he went running to the EC because he wants it retracted, rather than deal with the actual issue. The person who is looking like a fool is him.