As a data analyst that works with persons from around the world. It is challenging when the meaning of email address in data views does not currently correctly take into account local parts of email addresses (the part before the @) that includes characters beyond ASCII. The use of UTF-8 strings has been defined since at least 2012 and providers like gmail are allowing such strings to appear in the local part of an email address. Fixing this will allow more accurate evaluation of email addresses in a dataset, and fewer confessions as to data quality.
According to RFC 821 email addresses could only include a limited set of letters and numbers in the local part of the email address. However, that RFC has been superseded a number of times.