In my Japanese community, I want usernames to only consist of ASCII characters and numbers when users register. Therefore, I have disabled the unicode usernames feature, and the allowed unicode username characters input is also empty.
However, when creating new users, I have noticed that usernames can still include characters other than ASCII characters and numbers.
What could be the reason for this?
Is there a solution available to successfully restrict all characters except ASCII characters and numbers?
Update:
This bug also exists in my English community 
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