I wonder if it's the first time to enforce Chinese governance in Hong Kong's train station. Hung Hom, the current terminus of long distance trains between Mainland China and Hong Kong also has the same border inspection system with West Kowloon, the disputing new terminus.
Though Hung Hom is not announced to be under Chinese sovereignty, West Kowloon is now announced to be a part of Chinise territory.
It means there is no freedom of speech on the platforms in West Kowloon?