It seems to me that the first comment by the original poster should always be shown at the top, and top-level comments by other users are responses to that. This seems to be how all comment threads are treated by the community, and the current sorting algorithm makes them hard to follow if there are 10+ comments by the time you see the thread.
Oh, and you should be able to write your first comment before the thread is created.
Oh, and you should be able to write your first comment before the thread is created.