Maybe instead you have to be sponsored by somebody in order to view posts, but instead of banning people outright, let the sponsor's karma/reputation be affected by the people he sponsors. That way someone who creates a lot of value to the community can mentor someone who is not currently providing a lot of value, and help them understand the community or decide it isn't for them. Then if the relationship isn't working out the sponsor can stop sponsoring them and the person will have to look for a new sponsor if they want to do anything but view the stories and discussion, but the community will be kept fairly intact, except for the people the system is still trying to figure out or vice versa.