What happened is that many ccTLDs were resold at-will, and they've effectively lost all meaning.
Apparently, in addition to sounding like "new" in English, it sounds like a Norwegian word for "now", so both locales used it to make neat domain names... none of which have to do with the small island in the south Pacific named Niue.
I've had a blacklist in Flagfox for ccTLDs that get resold without regard to any nationality for quite a while, and ".nu" is one of the more recent additions. That said, it looks like I previously just used that blacklist for whether to show the notification (which is disabled in the current beta because the WebExtension notification system sucks), not for whether or not to show it in the tooltip at all. If I remember correctly, I don't think I intended for that to change, so it looks like I'll need to fix this. (also, I took the time to add in a giant list of internationalized TLDs that are nation-specific, so I should probably actually be using that new list) Thanks for reporting this. I'll fix it for a future version.
I want the info to all be shown together, in the proper context. It's always been in there and I don't intend to remove it. Also, if you navigate to an internationalized domain name, the address bar will show the address in whatever native text is needed for the language, and the Flagfox tooltip will show the official ASCII version of the domain name in punycode, so they're not always shown the same. (though, it looks like that only works in Firefox 57+) I need to find some more examples, but you can test that on this site for the ".Ñ€Ñ„" registrar (which apparently our current forum software can't tell is a URL): [url]http://ÐºÑ‚Ð¾.Ñ€Ñ„/eng/[/url]