It is a problem of java.util.Properties#store(OutputStream os, String comments) method. The comments parameter are not escaped. It causes then problems in IDE to read and show such file property to user when working in another locale (like chinese).

What is a reason not to escape comments to format \uXXXX?

If you dont agree it is an issue, explain how should be treated such a file?
###@###.### 2004-08-16

###@###.### 2004-11-15 20:08:06 GMT