I've been reading the Jira documentation on how to customise the content of Notification Emails in Jira, which seems to be to be quite involved, having to pull down the files individually and modify the XML then re-upload them.

Some issues listed recently have been marked by the Atlassian Team as 'Won't be Fixed' with the reason stated as being 'This feature will make Jira too complicated'.

This as far as I can tell is by far the most complicated part of Jira, and there is no need for it to be. A UI to allow Administrators to easily modify the content of email notifications would be a great feature to add.