Single Status Update
I wouldn't exactly call it weird. I use status updates on my profile to inform those interested about new Soundcloud publications with occasional micro discussions arising. To me that's exactly the right blend between public and private.
The only thing is that this is not so well documented; frequently people (like you) confuse the public feed and private messages and end up posting private matters on the public feed. It would help if there was a message box reminding one about the semi public nature before posting.
To stay really private, use the "message" button on another person's profile.
BTW, this geature's been around forever, eben before the forum overhaul.