At the moment, if you export a language file using "export to file" feature, it doesn't automatically "rebuild" the language file. So, for example, the spaces before "=>" marks aren't automatically matched with the English version, or things like that (order of the messages is, however, corrected upon export).
Version: unspecified
Severity: enhancement
Work around is running "php rebuildLanguage.php --lang=all" (or a language code of your choice. It's what I do after exporting in Betawiki. (php rebuildLanguage.php --lang=all --remove-unknown)
I think there is no need to integrate formatting of exported files at this time. It is project dependent and relies on external tools. Currently we have very little integration with exporting side. Maybe in far far far future, but not now.