Steps to reproduce:
- Anonymous source editing of any page with hidden categories and preview.
In the end used templates and effective categories will be listed.
Hidden categories become visible now.
- Is that intended?
- Did that has been all the time?
- IIRC some decades ago they were hidden for those who did not opt in.
- action=info does not mention any hidden for anybody (is that intended, BTW?)
- Perhaps the CSS code for display:none was lost during some CSS loading module refactoring?
- In source preview .hiddencats might be hidden per default, while on page view .mw-hidden-catlinks .mw-hidden-cats-hidden is hidden.
- Maybe somewhere a rule for .hiddencats is sleeping today, but not loaded?
Confusing and inconsistent anyway.
- Behaviour of hidden cats should be equal for all desktop presentations.
- I do know that on mobile there is a beta feature underway which splits into “thematic” and “organisatoric” (which are the hidden ones) categories for everybody.