One person probably rated a movie they hated 1 star, whereas someone else rated it 3 star or 4 star. The inconsistency makes it hard to build a model that works

One person probably rated a movie they hated 1 star, whereas someone else rated it 3 star or 4 star. The inconsistency makes it hard to build a model that works for everyone. Also, the current one technically has 3 state, down, up and no vote. That's much more explicit and easy to build a model around.