In the ru-wiki stopped working strict search for "ё". For example: " "ёё" " - search always corrects it as "её" - looking for "её" but is not looking for the requested "ёё". https://ru.wikipedia.org/w/index.php?title=Служебная:Поиск&profile=default&fulltext=Search&search=%22%D1%91%D1%91%22 Change search "mode" in settings does not change anything.
Topic on Extension talk:CirrusSearch
Note that the search settings in the user preference tabs affects only autocomplete: suggestions displayed while you type your search query. It does not change how results are found in normal fulltext search.
Folding of ё has been recently implemented and activated on russian wikipedia and causes the behavior you describe here.
If you need to distinguish between е and ё you now have to use advanced search keywords:
- simple source search: insource:ёё
- advanced regular expression search : insource:/трёхмерном/