Limiting posts' scope
If you want to limit the scope of your posts to just trusted members of TuscanyCircle, select the category named "Trusted" when you create the post. Make sure this it the only category you choose (because everybody can see all the other categories and they're ORed). For example, if you wish to discuss something of a somewhat personal nature, this would keep the post (and its comments) out of RSS feeds and search engines, and off the website unless the reader is logged in and trusted user. You can use email notification, also available only to trusted users, to supplement your RSS feeds containing public posts.
The list of trusted users is maintained by yours truly. It's a small group of users who have enough of a history with me for me to trust them on TuscanyCircle--i.e., they won't abuse the site or teach errant doctrines without being open to instruction and/or correction (I don't want to lead people astray), etc. To be fair, some may be relative strangers to other trusted users, but it would be likewise in most any small group setting at church, say, in the beginning.
Holler with questions.


RSS clarification
Really, the content of RSS feeds is determined by user access. If you're logged in when the RSS feed is fetched, it'll have the trusted-users-only posts in it. This assumes the logged-in state and the RSS-fetch operation occur via the same mechanism (e.g., Firefox). If you're logged in via Firefox but fetch the RSS via Google Reader, Google has no access to Firefox' cookies to know you're logged in, so the RSS fetch appears as an anonymous user (who doesn't have access to trusted posts). Clear as mud?