Sort:  

Musing is essentially rating your comments from their perspective through the use of their Upvotes. If they like your answer you'll get an upvote and the better the answer the better the upvote. However, I do see your point from the author's perspective about being able to show whether someone answered your question to your satisfaction but I'm not sure if that's something the platform intends to add or not.

Yes please! As of right now, all upvotes are decided by a team of about 5 curators who upvote posts depending on how good they thing something is. The problem with that answers are rated by one person, and if that one person doesn't understand your answer, you're SOL. Some way to have the people vote on how good an answer is would be perfect, and if the curator sees a 5/5 answer but doesn't understand why, they can leave it to another curator to review and decide that reward.

If the answer you get was helpful I don't think if it really matters anymore to rate the answer. You got the info you needed while the person offering got his upvote, if musing upvotes it. It's just a blockchain exchange of information. 

Well, it won't be a bad idea. It will be nice for those who asked questions to determine how helpful they find an answer. I think, it will also help other users

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.