I disagree with this attitude. Many demos such as this one with Quake code are intentionally looking for (funny) outliers by bending the rules. But this is not how anyone would use the system in a real scenario (no one should select license by typing "// Copyright\t" and selecting whatever gets auto-completed), so it doesn't really demonstrate any new limits besides what you could reasonably expect anyway (and what's mentioned on the Copilot's landing page).

Basically, in order to fall victim for this "code theft" (or any other "footguns" from Twitter threads) you'd need to be actively working against all the best practices and common sense. If you actually use it as a productivity tool (the way it is marketed) you'll remain in full control of your code.