I recently upgraded a Hudson server to 1.363. Today I noticed that リグレッション is displayed instead of "Regression", and 失敗 instead of "Failed"; e.g.
org.netbeans.modules.javacard.project.JCProjectTest.testDependencies (from JCProjectTest)
Failing for the past 3 builds (Since #63 )
Another server also upgraded to 1.363 does not exhibit this problem. And no other strings in the UI are in Japanese (that I have seen).
Needless to say, the server's locale is still unset (so defaulting to US/English). It is running Linux.
hudson.war!/WEB-INF/lib/hudson-core-1.363.jar looks normal to me; in hudson/tasks/junit/ it has Messages.class, Messages.properties, and Messages_ja.properties. "Publish JUnit test result report", apparently from the same properties file, is displayed normally in job/*/configure.
"OK" is also displayed instead of "Passed". My guess is that the enum CaseResult.Status was initialized during a request made from someone with a browser set to Japanese locale, and then these strings stuck.