Post-edit feedback

This feature is a test of whether giving post-edit feedback to Wikipedia editors enhances their experience, and which kind of feedback is best at motivating them to continue editing.

Current
Currently, one of two things happens when a user saves an edit:


 * 1) if the edit is successful, the page reloads in normal "read" mode
 * 2) the edit fails due to an error such as an edit conflict or loss of session data

There is no system feedback which explicitly confirms that the edit was successful, though if they are aware of it, editors may check the revision history.

Proposed
After an edit is saved successfully, a notification box will appear along with the read-mode of the page. This notification will give the editor a simple confirmation that the edit was saved, or another form of feedback related to their edit, such as how many readers it will reach, whether it is a milestone in their contribution history, or where it places them in relation to other editors of the page.

Feature requirements

 * Message will be displayed to user only after successfully saving an edit and the page is reloaded in read mode.
 * Message will appear in a notification box.
 * Message will display on the article page in one of three places:
 * aligned top and left with the chrome
 * aligned center horizontally, between the article/talk tabs and the article title
 * aligned center horizontal and vertical on the separator line beneath the article title if user clicked on main edit; aligned center horizontal and vertical on the section separator line if user clicked on section edit link.
 * If the edit was to a particular section, the notification will appear in the section.
 * Message will disappear after 20 seconds.
 * If the message is one that appears on every edit, users have ability to opt-out of further notifications

Experiment methodology and analysis requirements
See Meta