On a product page customers are able to leave review and star rating.
I set up a second store view and find out that all the existing reviews from first store view are not displaying in second store view. New review is showing only in store view where review was left by default as well.
Also I've noticed when opened a new review in Catalog – Reviews and Ratings – Customer reviews – Pending reviews there is a option to choose where a review is "Visible on". But editing hundreds of reviews to show in both store views would take too many time.