Text when converting PM to Topic doesn't work for login-required forums

How things are

At the moment, when a moderator converts a Private Message to a Topic, the following mini post is automatically put in the thread:

While this makes sense in a public forum such as meta.discourse.org, in our invite-only forum it causes much knicker-twisting as users mistakenly believe that the Topic has been published on the wider internet.

What I suggest

I have customised the text on our instance in order to mitigate this, but wonder if it would be better as the default text for everyone: