When you open a folder, and there is a pinned thread, the messages are display just like you had selected the thread, This happens even when there are no unread messages in the thread. This is confusing to me since, I then try to figure out what is new, within nothing is new.
I would prefer that no thread be selected; or perhaps the first thread with unread replies opened.
The pinned threads would remain visible at the top of the thread list.