I think the 'thank' you buttons are a great idea. I don't think so much of the stars as they only seem to increase with the number of posts. I think the stars should be scrapped.
If the stars were linked to the 'thank you' button, it would be fairer but still not perfect. But it would have an intangible side effect. I for one would find it very difficult to be negative about someone's post who I had just discovered had been sufficiently wise, kind and good as to thank me. I would be much more likely to be positive, perhaps even read it before replying.
I think it would build a more friendly community.
greg