> High performing participants in the stock market gain more influence in it. This is an optimising feedback loop for the economy and is less fair (but more effective) than simply giving everyone an equal say in the matter.

This assumes decisions which drive up the share price of Microsoft and/or the personal satisfaction of Bill Gates tends to yield better economic performance than decisions which represent what the public want. There's good reason to believe there are many situations where this isn't the case (the Gates Foundation's projects to help humanity are a thing, but so are battles for monopoly power). Wealth also tends to be much more heritable than entrepreneurial vision...