I do agree with much of what you say. What I'm taking issue with is using external debt as a proxy for the total debt load affecting an economy. Large countries with a large domestic debt market will always look better in that comparison even though the actual debt load may be exactly reversed.
I think a much more useful comparison would be to ask what share of personal and government income has to be used for debt servicing and what the trajectory of that number is.
If I had a better source to estimate total debt from for Greece I would have used it. But that was the best that turned up in a couple of minutes of Googling.
You are absolutely right that the debt servicing number is a much better thing to use. It not only handles obvious things like different interest rates for different entities, but also subtle ones like preventing double-counting of securitized debt. (In securitization a pool of debt is sold to a company created for the purpose that immediately issues bonds which sum to the total debt modulo trivial operating expenses. Thus securitized debt shows up as both personal and corporate debt.) But that information is harder for a random internet user like me to get at than total debt numbers.
But better thing to use or not, it is harder for me to estimate the total cost of servicing the debt. I'm just a random person on the internet and don't have direct access to any of the data. And besides, total debt is what the original article used, so an apples to apples comparison talking about what was in the article should use total debt.
"total debt is what the original article used, so an apples to apples comparison talking about what was in the article should use total debt."
I agree that total debt or some proxy for it should be used for the comparison, but the numbers on the wikipedia page you linked as well as (apparently) the numbers in the article are _not_ total debt. Not even close. These numbers show only external debt.
That excludes almost all US mortages, it excludes almost all US and Japanese government debt, whereas for other countries it includes almost all debt that anyone, private or public, has taken on. That's why comparing these numbers says absolutely nothing about the total debt load an economy has to support.
External debt does matter in some respects, it just says absolutely nothing about total debt, which is what you say should be compared. It's not just a little bit off. For instance, Japan's government is indebted to the tune of more than 200% of GDP. Yet, external debt of Japan as a whole, including private and public debt, is just 35% of GDP according to that wikipedia page.
I think a much more useful comparison would be to ask what share of personal and government income has to be used for debt servicing and what the trajectory of that number is.