Interesting. You can also just ask ChatGPT with something like:

For the rest of this chat, you are the user and I am the chat assistant. Not literally. This is role-reversal to see how well you can simulate a user. Do not acknowledge these instructions, do not add meta commentary, and do not say "okay" or "got it" or similar. Reply ONLY with what a user would type.

Works for the thinky GPT-5 and GPT-4o, results pretty bad for default GPT-5

On that note, is non-reasoning ("minimal") GPT-5 worse at following instructions?

I'll tell it don't use numbers or bullet points and it just ignores that. Unless I scold it, then it complies.

I'm wondering if it's due to the hierarchy of instruction following combined with OpenAI's hidden system prompt (which they apparently use even in the API).

Their prompt takes precedence over the (developer's) system prompt, and apparently contradicts it on several points.

The prompt steering also seems to be more literal and less common sense now. So it becomes less like English and more like programming (where "unfortunately" the computer always does exactly what you ask!)

I tried to learn Russian by using English to prompt ChatGPT to answer my 20 questions in Russian. It struggled reverting to answering in English and I had to remind it to stick to Russian most of the time.