This is SO important to have in mind, and the original author obviously didn’t:
“ Giving them a debt per capita of $80,000, yes each citizen of Japan technically owes $80,000” doesn’t make any sense since the Japanese government was smart enough NOT to borrow in US$ and because those interest-bearing assets are mainly held by Japanese entities.
So it would be more appropriate to say that each citizens on average owns the Yen-equivalent of 80kUS$.
As you point out, in Naira, the “fiscal space” is only limited by the resources available for Naira.
But there’s even more going wrong there: the author plots debt to GDP over time, without reflecting on it that a) it might not be debt that goes up but GDP that went down (the Greek situation), and b) comparing the two compares a stock to a flow variable.
So thanks for getting the train rolling on pointing out that this is misinformation.