Username Language Problem With Uppercase Transform

Hello,
I have a phpBB2 forum, https://innoctem.forum.st/
The language we use in the forum is Turkish but usernames are in English. I used text-transform:uppercase for usernames. In Turkish, capital letter for "i" is "İ" instead of "I" for example. So, this uppercase transform makes usernames a bit silly. Is there a way for me to define language as English for only usernames?

I attached the screenshot, thanks in advance.

When posting an image, you can either use the host an image button or insert image button.

So your forum is changing the English usernames?

Ah, ok, added the image as inserted to the message.
No, as my problem, my forum treats the names as Turkish, which I would like to define them as English. Without changing the forum language. Tho, I tried to changing forum language as well but somehow it didn't work too.

If the forum was made in Turkish then it will always be in Turkish if a member is English and they make the account in English then it will change for them but some things will still look strange to them if it's a name made by a member

So there is no way to predefine usernames as English? To get proper uppercase transform?

As far as I know No sorry.

Usernames will be whatever they use when creating their accounts.  I am confused what exactly is the issue.

The issue was language spesific characters. When using text-transform: uppercase, codes are self-defined from forum language as it is in a Turkish forum but I thought I should be able to put a code language definer at some location. I found a css code as 'font-language-override: "ENG";' but it didn't work, as least I couldn't manage. I wound some javascript codes, which I wasn't sure where to put them either. .

If it seems impossible, we can lock the topic down I assume. Thanks anyway.