When looking at reviews for applications without any reviews, there is no option to write a review.
I think this is a bug, not an intentional design. Still, +1.
Git commit 3dd3fed38b41f679d7a9748a8dd2d0a67758cd7d by Aleix Pol. Committed on 13/02/2018 at 02:05. Pushed by apol into branch 'Plasma/5.12'. Notify about the backend M +1 -1 libdiscover/ReviewsBackend/ReviewsModel.h https://commits.kde.org/discover/3dd3fed38b41f679d7a9748a8dd2d0a67758cd7d
I await the fix in 5.12.1!
Verified, works great!