Continuing the discussion from A little friendlier hidden post message?:
There’s lots of reasons why off-topic is distinct from other guideline violations. After all, Discourse development resulted in the idea of separating them already.
It would really make sense to have two different system messages overall instead of the simple one-line difference in the same overall message. If there’s reason to, the default messages could stay similar, but this would allow better customization of these quite-different flagging scenarios.
I suppose a workaround is to remove most of the system message and instead put long messages in the reasons line (although I suspect that won’t accept paragraphs and such, or at least is less amenable to that.