It would be a security and privacy nightmare!
Itch just does not have this infrastructure under the hood for anything that is multiplayer or player interaction. Exposing the account name to the public in any way is a terrible idea. Exposing it to amateur devs and scammers is also a terrible idea. You can attempt a login with that exposed name. Also, there are people with less than presentable account names or identifiyable account names - like real names. They might not want to see that name in a high score.