"Unread" for individual messages

[stiffmenot]

When browsing a topic, I want to see which individual messages are new -- as opposed to an icon on a board level that indicates the topic has new messages.

Have a "new" icon (or something similiar) appear next to each unread message.

The problem is to determine the specific messages the user viewed and those not viewed.  For example, a user might read messages 1-10 but not 11-25.  I suggest marking all posts in the topic as read after the user views the topic.  That's how the "You have new messages in a topic" icon works presently.  Either that, or limit the marked read messages to those that appear in certain pages viewed, if a topic has more than one page.

Has this been done before?