Except that this assumes there are no legitimate IDN domains on non-IDN TLDs. Considering how few IDN TLDs there are, I would wager that most IDN domains don't

Except that this assumes there are no legitimate IDN domains on non-IDN TLDs. Considering how few IDN TLDs there are, I would wager that most IDN domains don't live on these TLDs. However it seems they don't flat out block all IDN domains but only those containing the homoglyphs. IUIC they also don't block domains containing Cyrillic homoglyphs alongside other Cyrillic characters. This seems somewhat reasonable. I still think rendering Cyrillic in a way that makes alphabet mismatches more obvious would be a better and more future-proof solution.