If we change visible labels with the help of a hook or JS we should see what other extensions / gadgets could mess with what we are doing.

• HotCat - JavaScript gadget, changes how categories are rendered and provides buttons to quickly manage (source)
• CategoryTree - Provides a dynamic, collapsible tree for navigating categories. When the $wgCategoryTreeHijackPageCategories config is true, categories are rewritten on every page. It's set to false for Wikimedia wikis.
• navbox - Template often used to construct category navigation.
• MobileCategories - Performs an API call to get and display categories for a page. Only used for the mobile skin. (source)
• Navigationsleiste - Doesn't interfere with categories, but has a similar problem. e.g. {{NaviBlock | Navigationsleiste Träger des Nobelpreises in Physik}}.