Please read the use case below:

• user is starting edit some page (user knows that Confluence is saving draft every 30 seconds, so he/she continue editing, previewing, correcting the article)
• during editing, some trouble with network is happen - so sessions is expired now (user believes that Confluence is saving drafts - but it is not - as there is no auth. session)
• user press [Save] button
• user see Login screen

User data is loosed.

• User can try to enter his login data and login into Confluence, however "resumed" version of page is outdated (it was never saved after failure)
• User can press "back" button in browser, but text area form will be without user entered data.

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Implementation variant.

As submitting of draft document is performed from the client side, displaying of some icon that will indicate successful/failure commit can be very helpful.