It is silly to talk about equality of capital. Imagine a world in which everyone is equal.
And imagine a philosophical man or woman, gazing up at the clear blue sky and being filled with wondrous thoughts that bring her or him great utility. Thoughts that no amount of money can buy. A simpleton can see nothing there. How can we call this equal? The very blue sky above us is unequal.
But that is the sky - the thoughts come from within. True, but what is a javascript console, just some pale blue sky, to be filled with whatever you want. The simpleton can not derive any utility. A programmer can create anything. How can we call that equal?
But that is just some writing.
And if we let this person publish those thoughts, that script, that site? Then the simpleton can have nothing - the programmer, anything. How can that be equal?
There is no such thing as equality. There is only equal opportunity. Today, more than ever, nobody needs vast riches to achieve that. Perhaps everyone should have the chance to be well-educated, to learn whatever is within their capabilities, to choose to train for the best profession they can qualify for. But that is not "equality", in the sense discussed here.
Mark my words: so long as man can gaze up at a clear blue sky, as long as people are allowed to be friends and to talk, to think and to learn, to create, to share, to communicate - actual equality is a silly, misguided notion.
Look at opportunities - rather than capital results. Forget equality of capital, and look at equality of opportunity.
I'm only part way through the book, but to give a counterpoint from it, one of Piketty's examples is from a Balzac story, which describes a situation where basically those in the top 1% of jobs earn nothing compared to those with the top 1% of accumulated capital.
So imagine if you can't even earn money through a good invention because the money would go to the project's financiers instead of you. This is the sort of world Piketty is worried will return and stifle invention.
What kinds of opportunities? Who gets to decide? Should everyone be given some prime investment opportunities and the ability to make a lifechanging investment? That way, your entire decision and the outcome is based on you (including realizing that the market may or may not be rigged), but there's absolutely no risk to your current life if you make a bad investment choice. That's not an opportunity many people have.
You're still drawing lines in the sand whether you're talking about capital or opportunity equality. 'How much inequality is tolerable to the economy?' and other such questions. I haven't studied American capitalism much, but any system becomes weird when you can use/abuse the rules of the system to change the rules of the system. Eventually you start calling it something else.
One of the major points in the interview/book is the amount of inherited wealth, so to turn your example around, the programmer gets decent pay after building something of value while the simpleton who has contributed nothing has a mansion, several vacation homes and a fleet of vehicles. There can be some natural resentment when hearing that story and it's going to be a focus of the inequality debate.
Equality of opportunity was lost once pure ideas become patentable, and competition became a race for the largest pool of obscured threats backed by government force.