I hope everyone knows there's nothing binding about this page. It's just a page for extension authors to list their custom namespaces in order to avoid conflicting. Declaring 500-599 will only be used for custom site namespaces and any extension using them is wrong is just silly. Like Jack points out, SocialProfile has been using its 500-range namespaces for quite some time, and there's nothing wrong with this. He should be allowed to add his namespaces to the list like every other extension. Looking at the discussion above, I hardly call that a consensus. It's barely even a discussion, coupled with the fact that this is a very very low traffic talkpage. I don't see any developers involved in the discussion, and I don't remember the discussion being advertised on wikitech-l or mediawiki-l as I would expect.
Topic on Talk:Extension default namespaces
What's the big deal?
Agreed, this page has always only been a guide, never a rule. It's intended so that extensions adding new namespaces can try to collaborate and avoid forcing people to override default namespaces all the time because of extensions always overlapping. Every extension that defines a custom namespace should always have some method of configuring the extension to use different namespace numbers. And sites can define whatever manual namespace numbers they want and force extensions they install to use numbers that fit around that. The idea that 500-599 should be site specific is ridiculous even at a logical level... 1000+ would make more sense, 2000+ if we have to. Personally I have a site namespace of my own sitting at 112-113. Btw here Manual = 100, Extension = 102, API = 104. Frankly the 100-199 range has always made much more sense to me for site-specific namespaces. SMW is just an oddity which can have a config option set or we can just use the free ones around it.
Personally the thought that we should do away with this whole hardcoded namespace thing has been lingering in the back of my head for awhile. We really need some way for an extension to request a namespace on a first-come first-served basis such that after a number is reserved another extension will always get a different number even if the previous extension was uninstalled.
Wow... waitasecond, I even commented on just that right on this talkback 3 years ago. Btw, defining a range for Wikia to use without asking or even telling them feels like being the kid that draws a line in the sand taking 3/4 of the sandbox to himself then throws a temper tantrum when the neighbour's kid walks over it and tries to have fun with his other friends.