I wish it was allowed to have persian letter usernames maybe even symbols as usernames it looks really cool and increases the username pool as well.
I believe there is still an open issue on Github for this, but no one was interested to help implement and test it. So use the search function and contribute!
You won’t get non latin usernames anytime soon. But you can change the display name using non latin charactets
This thread is news to me. Unicode is Unicode, no? Why restrict to Latin letters?
There is also the risk of homograph attacks. The link below is for domain name encoding via IDN, but the same applies to usernames. You could easily impersonate another user by having chars that look similar.
Because URLs are usually in ASCII. That was a standard. Check RFC 1738 and 3986. Now, you can use percent encoding, but why use that. It just complicates things.