One has bought 1% of the coins and getting therefore 1% of new coins and transaction fees. His stake is growing in percentage to other (smaller) accounts, if he doesn't spend any coins.
You say he is getting richer all the time and POW is different?
If you read what I typed, the idea of compound interest in "stake" systems was only a secondary problem that was in addition to the main point.
I still see no difference in monopolization with stake size or hash rate. Both will make the richer get richer by itself.
Only if you burn the transaction fees (and maybe without interest/mining reward) it may not be the case.
But this kind of system would not attract enough people to success...