Here's a screen shot of a private Buzz post from how things were.
Here was no indication at all that the post was private.
Clicking on the word "Private" reveals to the viewer who has access to see the post.
What would be better is if there was a stronger visual indication that a post is not shared with the world.
In the screenshot I've simply highlighted the word private in red.
Edit: as Noble Ackerson pointed out red is currently used to highlight when a Buzz post is muted, so maybe a different colour to highlight private posts (like Green) would be better.
That seems logical and visually strong enough.
Do you post privately on Buzz? Scrolling through your posts on Buzz would it help you pick out what was private from what was public if posts were highlighted in such a way?