I’m not sure if this is the right place to write about this, but there’s something of the problem with the language detection (sorry, I don’t know the technical terms) module of several *MediaWiki* extensions and templates, such as the newly-released *Wikimedia Commons Upload Wizard* and... many templates!
For example, when I go over to the Upload Wizard for testing and casual uploading, there's a banner at the top telling me that the language was not found and that it “defaulted back to English”.
Obviously, this would not be a problem with a speaker of *British English*, but it could potentially be a problem in all sorts of frameworks with someone who picked a language code like “*arz*”—*Egyptian Arabic*, which would predictably default to English even though a *Standard Arabic* version of the tutorial is available, which the average *arz* speaker would definitely be more familiar with!
The problem, therefore, is how MediaWiki handles dialects as separate languages, and if it’s not fixed now, it could be a much bigger problem as the usability initiative affects more and more components of the website. Could some programmer fix this? I don't have the first clue about how PHP works... (sorry for the long post, by the way)