Yesterday evening I found out that the just installed engine for my diary had a "nice" security bug. When posting comments to entries that are not visible for everyone ( except for known users ) their comment is exposed to everyone in the RSS feeds for comments.
This bug however does not occur for the entries themselves. If you read the RSS feed for the entries you will see only those that are valid for your userlevel. But with comments, everyone sees everything.
Downside, this is not easily fixable - but the upside... I simply deactivated the feature of comment RSS in general. It now only shows the headlines and title for the entry in the feed, thus not exposing commented text to everyone anymore.