Thinking about this for a while, and the example of the Bolshevik refusal to pay the Tsar's debts brought me to realise that it actually isn't about what the debtor nation/government does or thinks - it's about the view of the creditors. This shows the beauty of getting a CB on defaulted loans - the creditor can act on a CB or not, at their option.FWIW this seems wrong. The entity which borrowed the money no longer exists. As for the people who live there, who probably lent the money, well, try not to get conquered in your next life. Finally, what country would ever annihilate another state in war (as opposed to peaceful diplomacy) and then pay their debts?
There probably does need to be some sort of "bad debt statute of limitations", though. Neither governments nor POPs are plausibly going to await their payback and keep gaining MIL for generations on a loan that's clearly not coming back...