Non-ASCII strings gets corrupted or just simply does not get posted in status updates and comments.
The default string operation functions do not support multi-byte text (virtually all non-english text). You can fix this problem by installing PHP’s Multi-byte String Library and setting mbstring.func_overload to 2 in php.ini
Starting in 3.08, we will attempt to force this to on in header.php (if the mbstring library is installed), however unless you are running a fully dedicated server, it will probably fail due to security restrictions. If it is not working, you will have to set it manually in php.ini
1 mbstring.func_overload 2
Non-standard php.ini (used by some hosts)
php_value mbstring.func_overload 2
Multi-byte text http://www.php.net/manual/en/book.mbstring.php