This is related to the above issue. When you import some issues to JIRA from a CSV file which contains Japanese user names, JIRA automatically creates those new user names in its database. However, these user names cannot be deleted, unless JIRA is restarted. The property useBodyEncodingForURI is already set to "true" in the server.xml file but a restart is needed. This should not be the case.

Support issue reference: https://support.atlassian.com/browse/JSP-7314