This got lost due to my confusion in T203864: Resetting a global preference via API does not work:
I can set custom (i.e. prefixed with userjs-) options globally, but I can't make them local again:
- Save userjs-foo=foo as global preference: https://de.wikipedia.org/wiki/Spezial:ApiSandbox#action=globalpreferences&format=json&change=userjs-foo%3Dfoo
- Confirm it is set properly: https://de.wikipedia.org/wiki/Spezial:ApiSandbox#action=query&format=json&meta=globalpreferences
- Remove userjs-foo as global preference: https://de.wikipedia.org/wiki/Spezial:ApiSandbox#action=globalpreferences&format=json&change=userjs-foo
- Repeat step 2.
(Don't forget to fill in the tokens in step 1 and 3.)
Expected: The preference should be gone.
Actual: It is still there, with the old value, even though step 3 complete with "success".