Why would you tell it is any persona? Is this the magical "prompt engineering"?

I haven't looked into this one but I've seen analysis about past reports that this has more to do with context pollution than any nefarious backdoor. If you pump an LLM prompt with irrelevant information it will just do worse. Some bits of irrelevant information will have a bigger impact than others, but in general it is a good practice to keep prompts detailed but relevant.

To surface trojan intentions in open models released with possibly hidden intention in mind.

It might be the case that the models internally predict the nationality of the user given other indicators, e.g. tells in the way they write.

You are a wizard you can cast level 9 Python skills.