You discovered the click and drag yet?
I was trying to reply to this post, at the same time you did. Instead of an edit conflict, it lost my post, as far as I can tell.
I was just trying to edit my post that you replied to there, and it did it again! It does it when you try to preview or post. It took me to a page that looks just like the full talkpage but has this thread missing, strangely. However, I found that I could go back in my browser and my post and edit box were still there.