The message wikibase-linkitem-alreadylinked has a link to the item page in the repository. This is convenient, but it should also link to the article that is already linked.
"mediawiki.jqueryMsg: wikibase-linkitem-alreadylinked: Parse error at position 115 in input: The page you wanted to link with is already attached to an [$1 item] on the central data repository which links to [[$2]] on this site. Items can only have one page per site attached. Please choose a different page to link with."