I'm an unapologetic ASCII bigot, at least in this space. It isn't just smartphones, it's been years since folks found unicode homographs (?), code points off in the weeds that look similar to ASCII characters, and started registering internationalized domain names (IDNs) for links to fool people into going to malicious sites.
I have all due respect for i18n given that I'm an English-speaker and can't read any other language, but getting i18n completely correct in complex user interfaces seems to be at least a little tricky, and end user interaction with email header data seems to be a tricky place. If this problem has been adequately solved and I'm just an ignorant old bigot, I'm hopeful that someone here will correct me.
