Testing deepcategory more thoroughly, we think there might be a problem related to umlauts.
See the examples:
`working`:
[[ https://de.wikipedia.org/w/index.php?cirrusUserTesting=explorer&search=deepcategory%3A%22Friedhof+in+Hamburg%22&title=Spezial:Suche&profile=default&fulltext=1&searchToken=2noilto638szmia3cvwkuqbe8 | deepcategory:"Friedhof in Hamburg" ]]
`not working`:
[[ https://de.wikipedia.org/w/index.php?cirrusUserTesting=explorer&search=deepcategory%3A%22Friedhof+in+K%C3%B6ln%22&title=Spezial:Suche&profile=default&fulltext=1&searchToken=11pxjf4otoevy0jrnznpmsj0t | deepcategory:"Friedhof in Köln" ]]
[[ https://de.wikipedia.org/w/index.php?cirrusUserTesting=explorer&search=deepcategory%3A%22Friedhof+in+M%C3%BCnster%22&title=Spezial:Suche&profile=default&fulltext=1&searchToken=dof0hluqojemy7yzoqe6ad01 | deepcategory:"Friedhof in Münster" ]]
All examples contain at most one subcategory with no further sub categories, but all contain articles.
This bug is blocking the inclusion of deepcategory search in advancedsearch