I totally agree that they tend to create a 'hive mind' type unity when there is a scalar value. That an be good in the sense that the community converges around a common set of shared beliefs and values, folks who don't share those beliefs and values get signaled to leave, and typically it seems they do. The 'center mass' of that community moves but only slowly over time.
In one of pg's posts about the challenges of karma and Hackernews, I suggested that an interesting experiment might be to try making it a vector rather than a scalar. The idea is conceptually simple, you have 'more approve' and 'less approve' (upvote and downvote) but the person whose comment you are posting on defines the vector. It would work like this:
Alice upvotes Bob generates vector [1, Bob] Alice downvotes Chuck generates vector [-1, Chuck] Bob upvotes Alice generates [1, Alice] Chuck dowvotes Bob [-1, Bob]
So between Alice and Bob there are both positive upvotes. This creates a [Alice, Bob] nexus, there are negative votes away from Chuck by both Bob and Alice which creates a [Chuck, Chuck] nexus which is directionally 'opposite' the [Alice, Bob] nexus.
Now if you work this over the community. Alice and Bob will have higher karma in the [Alice, Bob] community and lower in the [Chuck, Chuck] community. So when you show karma 'points' for Alice they represent Alice's conformance to that community and show Chuck as negative in their community. But when Chuck looks at his karma he is positive in the [Chuck, Chuck] nexus and Alice and Bob are negative.
The question (and I don't know the answer of course)is whether or not you can create a discussion site which evolves several simultaneous communities by karma score within the same set of conversations. The ultimate test would be that the comments you see are always interesting and insightful to you but they may be differently rated than someone else seeing the same conversation.
Anyway, one of those 'if I had a spare weekend I'd try this...' kinds of thoughts. The idea is public domain, I've got not personal claim on it, I'm not even sure its implementable!