Most forums and many websites (like gmail) are able to save your post in a cookie as you type. If you navigate away by mistake, the post will be waiting for you if you go right back.
Does the billion dollar forum have that feature?
Yes
[sort of]... Last time I checked, Epochtalk had an autosave feature that kept triggering every 10 seconds, so you're still going to lose everything that you'd type within that time frame.
- It's worth noting that it's not fully automated (you'd still have to accept a pop-up notification in order for it to load the latest draft).