This is still (probably) a draw from the US economy on net. Unless the institution is offsetting it somehow or is somehow not a part of the US economy.
> do I owe... taxpayers... Microsoft?... remuneration?
If Microsoft paid a lot to train you up and you leave before they get that value back, then they may want you to repay them.
That's generally not how things are done, but if the learn-and-run thing that this article talks about were to spread more into private industries, I can imagine private companies either paying less during the first N months or having minimum-term work-contracts with early-termination fees.
Who's going to pay back societies that send off educated, healthy young adults to the US economy? The value invested in individuals does not accrue all at once while they are at university.
It makes zero sense to try and balance the value at level of individuals. It is better to look at it at a larger scale (tens of thousands to millions) and approximate the value of what's coming in and leaving. There is a lot of guess-work involved, especially around future-value. There are no precise control-knobs to get the exact number and caliber of people you want; the best countries can do is set policies and hope for the best, without accounting for second and third order effects.