Edit: For some reason this keeps bouncing around in my head and the more I think about the more I believe that Emma should have contacted you privately (at first, anyway) instead of jumping right into attempting to publicly shame you.
The issue tracker for kbin codebase was the correct place to submit the complaint.
Licensing issues are tricky and if you're the copyright holder there's no way to know if people stealing your code are acting in good faith or not. Best course of action is to document and report the violations "officially". You need to have a clear track record in case the other part is going to try to deny or obfuscate the situation.
It was the right thing to do.
As for the tone and the username.
From what I can see, she's the main dev for that codebase and has been for many, many years. She gets to decide the tone, she's the one who's defending her rights and work.
Having said that, ernest handled it well - and is clearly acting in good faith. So that should be the end of that.