Just as a further side note, if you really want to refute the ponzi allegation, this is the question you have to answer, becasue nothing else is directly relevant.

What would be the effect of making it so that value can only flow outwards? If it still works then, then its not a ponzi. Because thats what a ponzi scheme is, an economic system that endures by using incoming value, intended as capital investment, as outgoing revenue stream to pay liabilities created by previous investments.

That means no exchange of fait for SBD or steem, no powering up, no new accounts, no buying SBD with steem.

If the streets only go one way (out) and it still works, then you don't have a ponzi scheme.