I can enter Asian language characters correctly as comments in HDL or other text files using the ISE Text Editor.
However, after I save the file and open it again, these characters become corrupted and are not displayed correctly.
If a file contains more than 50 lines, it has been observed that some Asian language (Traditional Chinese, Simplified Chinese , and Korean) characters are not displayed properly in the ISE Text Editor after the file is closed and reopened. Typically, Asian characters occurring after line 50 might be corrupted (unreadable) in the ISE Text Editor.
This issue was resolved for Japanese characters in ISE 9.2.04i. See (Xilinx Answer 29853).
For Traditional Chinese characters, Simplified Chinese characters, and Korean characters, this issue still exists. To see the correct characters, the same file can be opened in another Text Editor (for example, MS Word).
To use a 3rd party editor within Project Navigator, click Edit -> Preferences and select Editors under ISE General. For more details, please see (Xilinx Answer 13713).
All issues mentioned above have been resolved in ISE 11.1.