And yet, despite this being a frequently recommended pro tip these days, neither OpenAI nor Anthropic seem to shy away from using "do not" / "does not" in their system prompts. By my quick count, 20+ negative commands in Anthropic's (official) Opus system prompt and 15+ in OpenAI's (purported) GPT-5 system prompt. Of course there are a lot of positive directions as well but OpenAI in particular still seems to rely on a lot of ALL CAPS and *emphasis*.

https://docs.anthropic.com/en/release-notes/system-prompts#a...

https://www.reddit.com/r/PromptEngineering/comments/1mknun8/...