Nice one, you're the man!
For Metawiki use "m" prefix.
I'll keep that in mind for the future. If this is about my user page, it looks like interwiki links don't work if you pass parameters to the special page. That's why I went with an external link.
Yes, they don't work. But you can write [[Meta:Special:CentralAuth/Jkmartindale]].
Or Just Special:CentralAuth/Jkmartindale, since the CentralAuth special page works on all wikis, not just metawiki.
Adding translatable templates
I'm sitting in a bedding store in Taiwan waiting for somebody to fly in, so it's not like I have anything better to do with my time.