When an issue is created or modified by a user, it will be marked as an unread issue for the other. When user selects that issue in the Issue List, it is then marked as read. This works just like in emails. Unread issues are marked as in the Issue List.
During its lifecycle, whenever an issue is modified, it is marked as Unread. And, it remains unread until the user reads it. Also, note that different users will have different Issues marked as unread.
User can filter unread issues.
User can mark a batch of issues read or unread.