A well written Idea, and we are solving for precisely this. There will be some sort of method (likely an API. for developers to build data migration tools) that allows the conversation history for a ticket to be imported alongside a ticket and show up in Help Desk in Customer Portal alongside new tickets. This will be because the conversation messages will be imported into the same data model as any other channel connected to Help Desk or Inbox (e.g. Live Chat, Email, WhatsApp), not just as objects on an activity timeline.