It's because Unicode don't allow for language switching. It takes up to eight bytes per character in Unicode if you want to support both Chinese and Japanese i

It's because Unicode don't allow for language switching. It takes up to eight bytes per character in Unicode if you want to support both Chinese and Japanese in a single font using IVS(and I don't think there's any font that actually supports this). AFAICS(As far as I can search), Simplified(PRC) and Traditional(Taiwan) Chinese encoding are respectively called GB2312 and Big5, and they're both two byte encodings with good practical coverage. Same applies for Japanese Shift_JIS. If e.g. :flag_cc: were allowed to be used as start-of-language marker, one could theoretically cut that back down to two bytes per character without losing much and actually improving language supports.