Truth be told this is not really a bad idea but with the reward system in place I don't see the need for it. It's also worth noting that "answers" being voted by the account @musing are done by human manual curators, so in itself it's already a basis as to how helpful or not the answer was.
Also, from what I'm seeing, a lot of people are in Musing for the upvotes, if the star system would likely affect the upvote given by the @musing account then people would also most likely game that one. So I think there really is no need for it.