Hello from Russia!
We are have permanent problems with resolve cyrillic symbols in usernames, who send request by email. For example, name "Польский Артем" look like "=?UTF-8?B?0J/QvtC70YzRgdC60LjQuSDQkNGA0YLQtdC8?=" - see attach. I think this applies to the Chinese symbols, and others.
Please, check it and resolve.
If possible, repair the incorrect names in the database as well. If this field contains "=? UTF-8" means you can it change! I do not want to do it manually.