I can't write @ in the chat. It works like Ctrl+v in the game.

What keyboard layout are you using?

Happens with Czech keyboard layout, bug works as intended probabbly, it's caused by Java 8, in Java 7 it doesn't happen. It must be a keyboard layout, where Right Alt + V = @, but Right Alt acts as Ctrl + Alt, so Java interprets it as Ctrl + V. So nothing you can fix most probabbly.

That sounds plausible, so for the moment I will mark this as invalid.