I feel like this is a browser UX problem, right? A browser designed to prevent phishing of readers of both ASCII and non-ASCII languages might display both the

I feel like this is a browser UX problem, right? A browser designed to prevent phishing of readers of both ASCII and non-ASCII languages might display both the punycode and unicode versions of a website, and if a heuristic is detected that a homograph is used that would otherwise result in an Alexa Top 100k site, display a dialog to warn against a phishing attack. (Your flüge.de example shouldn't trigger that warning, for instance.) https://github.com/phishai/phish-protect https://github.com/phishai/phish-protect is an attempt to do this, but I think there's a better middle ground for international users that doesn't simply block-by-default all punycode domains.