View Modes / Filters
Only show starred items. The subscriptions list will only show feeds containing starred articles. The count displayed is the number of starred items.
Only show unread items. The subscriptions list will only show feeds containing unread articles. The count displayed is the number of unread items.
Show all items. The subscriptions list will show all feeds. The count displayed is the number of unread items.
If you don't want Reeder to display unread or starred counts in the app, you can disable these, see "Settings"→"App Settings".
Reeder by default opens folders as a list of feeds. A tap on the button on the right (the one containing the unread or starred count) will open the folder as a list of articles. This behavior can be switched, see "Settings"→"App Settings".
Posting to QUOTE.fm works by selecting text in the article or web page. Tapping on "Share…" will then open the sharing panel, listing all services which can share text selections, one of them being QUOTE.fm.
Reeder 3 makes use of the Twitter integration in iOS 5. If the Twitter button is missing in the sharing panel, please make sure that you have added your account(s) in "Settings.app"→"Twitter".
Toggle un/read or un/starred Swipe right/left on an entry in the article list (configurable, see "Settings"→"App Settings")
Mark articles above/below as read Two finger swipe up/down
Back to the articles list Swipe right
Open article in the in-app browser Swipe left
Toggle Readability Pinch to zoom on the article view
Full screen image viewer Pinch to zoom on any image
Image sharing options Tap on any image
Link sharing options Tap and hold on any link
This help section will probably not answer all questions. Feel free to contact me if there are questions which are not covered here. I'll try my best to update this section with more answers if needed.