Email highlighting in console output is superfluous to say the least.
Not only is that dark-blue-on-a-dark-gray-background quite unreadable, but there’s really no need to linkify email addresses in the console output window.
I’m swithing back to the light theme next week, we’ll see how that goes.
I think it is just matter of your browser settings.
I wrote a valid email in my stderr and I had not the same problem.
This one’s not program stderr, it’s compiler (error) output.
Here’s a case that’s easier to reproduce, as a C program:
Using a different browser, because obviously it’s my browser settings.
You are right, it seems codingame is doing that on compile error messages.
My test was not so accurate, I apologise for doubting you.
Good news everyone, it will be fixed soon!