I removed the statement. For one thing, the "capitale nationale" as a nickname is dubious (it's more of a description). I know some people consider Québec City to be a national capital (this is a political/cultural issue), but it's not the expression they use as a nickname for the city (that would be "la vieille capitale"). Second, the source has no "official value" and does not address any nickname issue. The whole Québec is a nation and Québec City is its capital debate, I believe, should be left out of this article. It's a can of worms that'll only bring confusion and edit wars. Québec City is in the administrative region (division) called Capitale-Nationale. That's all we can say that is relevant.