If you look at a ChatZilla commit, e.g. https://www.ohloh.net/p/chatzilla/commits/143991363, and then look at the source, e.g. http://hg.mozilla.org/chatzilla/file/779a91a4c736/xul/content/menus.js, it's clear why Ohcount is registering it as C++. But it's wrong, massively.
I didn't set up these modelines, don't use them and don't think 'fixing' them will help - Ohloh has a massive, completely incorrect history of languages for the ChatZilla project.
I personally think that the modeline should be secondary to unambigious file extensions (especially when in direct conflict).
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