Thread:Support/what does upstream have to do if a key is changed?/reply

Sounds like not. I added a FAQ entry on this:
 * FAQ

Also related:
 * FAQ

Snippet from #mediawiki-i18n (edited by me): [15:37] is it possible to rename a key? for instance, we                    want to do this for http://mifosforge.jira.com/browse/MIFOS-3906 [15:42] <+siebrand> meonkeys: basically you should *not* be held back because of L10n. Renaming keys is an easy operation from a development perspactive, so when there is a                    good reason to do it, do it. [15:42] <+siebrand> meonkeys: just don't do it frivolously, because it                    takes some work, although not much.