The only setting up for languages that I have is that various
keyboards are enabled -- at the moment, (in order in the popup) Greek,
English, Syriac, Amharic, Arabic, Oriya, Chinese (Trad), Chinese
(Simp), Tibetan, Mongolian, and BabelStone.
Maybe it refers to the little characters placed alongside Chinese
characters to assist with pronunciation (in Japanese they're called
furigana) -- most often, those extra "typography" features have to do
with Japanese (sort of like headers -- if you've ever turned Japanese
on, they never go away)..
aswalleh's name suggests that he's looking for diacritics in Arabic or
Persian; that might mean the vowel symbols that are usually not used
in writing ordinary text. But we ought to find out whether he wants
diacritics to be the same as or different from the letters!
Do you use Polytonic Greek, or Modern Greek?