While fixing 7042475, I found that the root cause of the problem for extra mnemonic label for ja/zh_CN on "JConsole User Guide" on "About JConsole" dialog is because of the un-needed resource:
        {"Help.AboutDialog.userGuideLink.mnemonic", 'U'},
which was supposely related to
        {"Help.AboutDialog.userGuideLink", "JConsole User Guide:<br>{0}"},

When performing translation, these resources are automatically associated and we automatically add (U) to the end of translation for Asian locales if the character was not available in the string.

Another related issue is that the link points to jdk6 doc
        {"Help.AboutDialog.userGuideLink.url", "http://java.sun.com/javase/6/docs/technotes/guides/management/jconsole.html"},