Duplicated nicknames with different case of letters

Helllo and helllo,

 

https://sessionserver.mojang.com/session/minecraft/profile/7211ae0b-db3f-4680-ae7c-b34f2c4befc0

https://sessionserver.mojang.com/session/minecraft/profile/ba5d76c5-d2fb-41c4-88e7-f54552632f7d

These users have the same nicknames, but with the different case of letters. How it is possible? Is there any possibility to fix this bug in the entire database to prevent any problems on Java Edition servers?

 

Best Regards,

k0l0r3k99