This should be ON by default, in my opinion. Also, I believe Mozilla has a massive opportunity here to demarcate themselves as the more security-conscious browser vendor. “This phishing trick works on all major browsers except Firefox” would be great publicity material.
That’s true. Also I guess domain names in most ideogram-based languages cannot be meaningfully converted to ASCII. The best detection method I’m aware of is detecting a mix of different alphabets in the domain, but I imagine even this has a lot of false positives