[oreilly]

Use the same system that decays a post's weight on the front page to decay a comments weight on a thread.

This will balance out the uneven distribution of karma that is talked about above, as new comments will be seen and given a chance to voted on even well into a conversation.

Having done this, comments that stop being relevant to the conversation should drop to the bottom and naturally attract less attention. Ideally, this will leave trolling posts ignored. (This can be helped further by having user selected timeout apply. If comment / responses are mapped as a tree, hide all branches that have no new activity for the past x hours, allowing users to change x as they choose. Give visual feedback to a comments age by fading old comments)

This solves the 'income' end of the system, as karma should now be distributed a little more evenly over time.