Yes, Some FTP servers are not supported. There are so many FTP server software and all of them are a little different. There is a FTP standard most FTP Server do not follow it completely.
By default the same character set as Windows is using is used. But if Windows and the FTP Server you connect to are using different character set, It can fail.
MC also support UTF-8 for international characters. If the FTP server announce that it support it. Supporting international characters where Windows and the Server are different and UTF8 is not used are a mess and that are not currently supported.
