In a Microsoft Exchange Server 2013 environment, you use the New-PublicFolderMoveRequest cmdlet to move a public folder to a different public folder mailbox. In this situation, the read/unread state for each user is wiped out for all folders in the target mailbox.
This problem occurs because of a function logic issue in Exchange Server 2013.
To resolve this issue, install Cumulative Update 7 for Exchange Server 2013.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.