In case you haven't noticed or don't know how to use it, here is how auto save works:
When you edit a post, your draft will be saved on the server automatically every 60 seconds. If you lose your input due to browser/computer crash or accidental clicks, you can restore your input when you revisit the same thread. This also works with new thread, simply reopen a 'New Thread' page, you will see the link 'Restore auto-saved content'.