Thread:Talk:Extension default namespaces/Social tools' namespaces/reply (6)

The "prior agreement" was based on the assumption that no extensions used that range, which as it turns out was incorrect. 500 was already in use by the extension before that "agreement" between three people occurred. I've checked Wikia's repository and it was indeed using namespace 500, before your attempt to "reserve" the range. This is not a "future" extension, it's a preexisting extension that has been cleaned up and added to the official Wikimedia repo.