Gets very confusing when the original message has had both top and bottom
posted replies!

I think the bottom posting argument would be fine if you could guarantee
that the whole thread was always contained within the latest message.
Invariably this is not the case, so one ends up sequentially reading each
post. In this case, it is actually easier to read top posts, as you don't
need to scroll down within every message in the thread.

Perhaps all newsreaders should offer the option of how to treat replies,
top-post, or bottom-post. There is already an option not to include the
original message in the reply, perhaps it would be better if this was the
default.

Stuart