Here's a potential patch for that particular issue: Use a special token for "AI Instruction" that is always stripped from user text before it's shown to the model.
The AI has no memory of what happened other than the transcript, and when it reads a transcript with multiple delimiters in use, it's not necessarily going to follow any particular escaping rules to figure out which delimiters to ignore.
This may just be an artifact of current implementations, or it may be a hard problem for LLMs in general.