it's supposed to do a save triggered by a browser close tab close, game close event.
yet another thing that is 'supposed' to work.

here's a direct quote of Nick: "In addition to saving during important events during gameplay, the game also forces a save when you close the tab/window."
and later on in the trouble ticket: "My only thought is that you might have had some internet latency, causing the save call to lag, and by turning off/sleeping/hibernating your computer, you interrupted the save call."

On a similar but unrelated note. I'd love the ability to save a main quest mid-stream in order to do a special event quest. The last two or three events have all come around the point where i'm nearing the end of a long main quest but the difficulty has ramped up so much that it still takes 5 or 6 days for me to finish it (thereby cutting into the time to do the special events). I know I could just reset and start the big quest over after the event, but who wants to do that when you are at level 320 of 350 (for example). And the events are coming so frequently that if I did that i might end up restarting things two or three times. (not that i'm complaining about the having a lot of events)