As I see it the purpose of safety training is to make it so that if I run a service where I return model outputs to innocent users it's not going to say things that will get me in trouble (swear at them, recommend they commit a crime, and so on). This is important if you want to run a user facing model and your reputation depends on what it says.

That threat model includes the user putting nonsense in the "user" turn of the model. It doesn't include the user putting things in the "assistant" turn of the model, that's not something a responsible/normal UI exposes. So... this quote-unquote attack seems uninteresting. It's like getting root access by executing a suid binary that you set up on the system as root.