I can't speak for mobile platforms or tablets, but we've implemented a type of "auto save" feature as requested. It requires a modern web browser (so if you're still stuck on IE 6 or 7, sorry, you're out of luck).

What happens is it saves whatever you're typing into your web browser's datastore. If you lose the connection, or your browser crashes or something, it should still be there when you navigate back to the page you were typing the text.

Try it! Type in some text in the quick reply box to this thread, then wait a few seconds (to give it time to store it). Then close the window without hitting "post." Reopen your browser and navigate back to this thread, and you should see the text you typed in still in the quick reply box...

DocJohn