I thought your basic argument was sound, but having read through the conversation twice, you might not be putting it in the best light. Your point seems to be that value can be extracted from capital and that is a substitute for value from labour. Seems good to me. But you then went with a gold-based example. Gold is money which is not really a productive form of capital because there is almost literally no way to extract value from gold. It is inert.

The value of gold is it makes the holder indistinguishable from someone who had enough resources to procure yea much gold. A useful signal in a healthy economy. But it was asking for the literal on-an-island example where there was no otherwise healthy economy. Since your argument depends on productive investment of capital IMO you should have hammered on that a bit more rather than trying to bring gold into the picture.

I'm seeing a lot of misconceptions about debt in this thread. It isn't possible to "burden" "unborn generations" with debt, they can always just renege on paying. The problem is what we see in the US, where the debt in financial markets is reflected in the real world by ... massive capital formation overseas in China. So the damage has already been done, unborn generations won't have access to the capital needed to live the lifestyle of their debtor parents. This is because the parents never built the capital to sustain their own lifestyle and eventually the capitalists will stop donating free stuff to debtors. IE, debt isn't a future problem to be paid back. The problem is always in the capital formation of the present and past. It is the future consequence of what capital got invested in, where & why. In that sense high debt can be good or bad depending on how much went in to capital formation and whether the capital is productive. But typically high debt matches to poor choices deploying capital.