Hello,

In Turkish upper-case version of i is "I with dot above" (0130;LATIN
CAPITAL LETTER I WITH DOT ABOVE) which is a multibyte character. A
single byte character is converted to a multi-byte character.  Also
lowercasing I in Turkish produce "i without the dot above" (0131;LATIN
SMALL LETTER DOTLESS I).

I think, as a matter of fact that GNU Emacs can't handle this multi-byte
to single-byte (and viceversa) conversion the problem arise. Using
upcase and downcase functions in Turkish doesn't produce a correct
result.

I think the problematic function is casefiddle.c:casify_object().

best regards,
-- 
Baris Metin
http://www.metin.org