Google Plus – How to Make a Post Public Without Showing on Others’ Streams

This has been fixed recently. Go to your Circles, right click on the circle you want to throttle or mute, and select "Show stream from this circle". At the top of the stream you will notice a slider that lets you adjust how much you want to see from that stream, including all and nothing.

In composing and editing the question, I might have come up with the answer myself:

• "Public" doesn't broadcast my post as widely as "Extended Circles" does. Yes, it's available but only to those who actively come looking.
• "Extended Circles" broadcasts my post not only to my circles but also to theirs. This gives me more visibility. But strangers can't see the post even if they come looking, unless they happen to be only semi-strangers because they are in the "extended circles".

So "Public" provides availability while "Extended circles" provides distribution. These are separate traits.

Frankly though, why would I write something that semi-strangers may read, but total strangers may not? That is what the "Extended circles" does, and it doesn't make much sense to me. So in essence, I would always use both in combination.