So... I've done about 10 more posts that I've given up on. Often, I'll hit the quick reply button on a thread, type up a long response and then click the "Reply to Thread" button that's just underneath the text I've typed up. That link will take you to the "Non-quick reply" page and as a side-effect blows away all the text you've typed. It drives me nuts.
If there's any way to fix this, it would really help...