The message blueprint-left-nav is * [[Main Page]].
When translating it, if the link target is translated, then translatewiki displays a warning that the link to [[Main Page]] doesn't appear and makes the message fuzzy. Maybe translatewiki could be configured to ignore this warning, but it sounds more right to me to make the message truly localized by reusing the actual title of the main page in the relevant language, so that the translators wouldn't have to deal with it at all.