This is such an interesting topic, thank you for providing a thoughtful overview.
I find it fascinating how differently people interpret the basic five-star rating system depending on the context in which they encounter it. If I'm searching for or reviewing a restaurant on Google, I'm aiming for five stars unless there was a significant problem, but that means that both, a Michelin star (another rating) restaurant and my local take-away would get the same rating, and I definitely prefer one over the other.
On the other hand, when I'm checking in beers on Untapped, I'll give an average beer a 2.5 stars, so I can easily find my favourites even after hundreds of checkins.
I also read that there are significant cultural differences, as most Westerners treat five-star rating system like school grades and aim for the top mark, while Asians (think the article was focussed on Japan) tend to give three starts for anything that was good but didn't exceed their expectations! Isn't it fascinating how the same widely adopted system has such different meaning in different cultures and contexts?