CentralNotice banners are displayed per language. We usually mean for a Polish translation of a banner to be displayed at the Polish Wikipedia, the German translation to be displayed at the German Wikipedia, etc.
If Universal Language Selector is set to use the same language as the wiki's content language, then this works as expected.
However, if ULS is set to use a language that does not match the content language of the wiki (e.g., English on the Polish Wikipedia), then ULS's language is the one that determines which translation of a banner you see (probably good) and, for banners that are not applicable to 100% of projects, whether you see one at all (bad).
This means that a banner intended only for the German Wikipedia will display for any German-using editor at any of the Wikipedias (e.g., Chinese), and that a Chinese-language banner intended for all editors at the Chinese Wikipedia will not be displayed to anyone who has changed the ULS settings to anything other than Chinese.