Dropping accents for category indexes 

For sorting. See Wikipedia:Categorization#Category sorting. From the page:

Don't forget to convert letters with diacritics, or non-standard letters to the nearest standard letters (that is: "standard" in English, at the time Wikipedia is written), examples:
Diacritics are omitted: e.g. Étretat: [[Category:Communes of Seine-Maritime|Etretat]], or: Ål: [[Category:Municipalities of Norway|Al]]
Ligatures are separated: e.g. Æsir: [[Category:Norse mythology|Aesir]]
Sometimes which is appropriate depends on the language e.g.:
From the Bruno K. Öijer article: [[Category:Living people|Oijer, Bruno K.]].  From the Ötzi the Iceman article:[[Category:Mummies|Oetzi the Iceman]] (in this case the German umlaut on the O is expanded to an "e" - preferably only omit the diacritic, without applying foreign rules that could make collation seem illogic in English: [[Category:Mummies|Otzi the Iceman]].
From the Arne Åhman article: [[Category:Swedish athletes|Ahman, Arne]].  From the Lasse Åberg article: [[Category:Swedish film directors|Aaberg, Lasse]] (Contrary to the previous example the "Å" is here expanded to "Aa" - again, better to only omit the diacritic, to avoid collation confusion in English: [[Category:Swedish film directors|Aberg, Lasse]].