Moderators (requests and notices)

It's more than 'disappointing'.

I have an expectation that posts I have made in non-public areas of the forum are not made public.

The privacy policy makes it clear posts are considered personal information:

We describe the categories of personal information we collect in more detail below:
...
Comments and opinions: such as comments and opinions you leave on the forum

and then describes where they will be made available:

How we use your information
We will also use your personal information for the purposes specifically described below:
...
Comments and opinions: we will display your public comments, opinions and responses on the public areas of the forum. We will not publicly display your private messages or private interactions with us or another user.

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Edit follows:

It then goes on to say:

Changes to this policy
We may update this privacy policy from time to time and so you should review this policy periodically. When we change this privacy policy in a material way, we will update the "last modified" date at the bottom of this privacy policy. Changes to this privacy policy are effective when they are posted on this page.

But there have been no updates, more recently than one 10 years ago, as far as I can see.

I'm now spending part of Christmas Day removing information about me that I never intended to be public. It's already been made public, of course, and may well have been compiled into archives.