That works for regular computer programs, but the problem is that the user can invent a different delimiter and the AI will "play along" and start using that on

That works for regular computer programs, but the problem is that the user can invent a different delimiter and the AI will "play along" and start using that one too. 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.