Rob Hooft wrote:

On the nl: wikipedia we are discussing the introduction of some custom {{msg:xxx}} templates. During that discussion it occured to me that this may be another namespace with two goals: internal messages for the mediawiki software, plus templates for in the wikitext. If we make a new message MediaWiki:weg on nl:, or MediaWiki:abc, who tells me that this will not conflict with a future built-in message? Do we need two separate namespaces for these features?

It's a good point. If a new internal message is created with the same name as an existing custom one, the custom message will replace the internal message when the new feature executes. It may be a good idea to write a script to search existing implementations for name availability, so that developers can check for conflicts before they choose their message names.

-- Tim Starling