Comment by drdaeman

> Does Russian alphabet have Є letter?

This should resolve your confusion: https://en.wikipedia.org/wiki/Ukrainian_Ye#Old_Slavonic.2C_O...

I believe, U+0415 ("E") is a valid character to use there. Sadly, there's no way to denote that the text is in Old Slavonic and should use different script so this "E" would be rendered visually similar to "Є".

While Unicode code points typically correspond to graphemes, that's not always true. Similar issues exist with Chinese, Japanese and Korean languages, as Unicode (see https://en.wikipedia.org/wiki/Han_unification#Graphemes_vers... - it has an example with Latin small letter "a")