I have had it happen with chrome, safari and explorer. I think it is a time out issue. It seems that the log out happens regardless of browsing. Maybe the 30 minute inactivity thing is if you are not posting it doesn't acknowledge activity.

This is nothing new. It has worked that way for years. Usually I copy before I hit submit that way if it has reached the time out I do not loose it.

On other sites if you have timed out, you re log in and your post is still there to submit. Here it disapears.