Use tags per user

Most people that use tags want them to sync over different users for the same account.
This is a problem to me. I am forwarding many mails to a single mailbox that many users share so User A doesnt’ want a message to be marked as read from User B.
This is the default behavior for IMAP. However, can I use tags that do not sync over different users/clients to identify wich messages a user read?