Oooohhh..
Someone needs to change MediaWiki:boardvote_nosession ,
boardvote_notqualified , and boardvote_notloggedin to tell people to
go back to their home Wiki to vote.
MediaWiki:Boardvote_nosession already does say that.
MediaWiki:Boardvote_notloggedin is only displayed on the source wiki, and
will match the wiki login status. I've changed the English version of
MediaWiki:Boardvote_notqualified.
I've also changed the link in the site notice on meta to go to a clearer
intermediate page.
-- Tim Starling