I read this paper by Acemoglu and Robinson right after I read the book by Piketty thinking that there would be some interesting economic debate. Unfortunately I was proved wrong and this seems to be exemplary for the stagnation of the economic field.
It’s extremely selective nitpicking, some qualms with definitions and arguing about semantics. In those places where Piketty actually writes the same thing as them, they don’t mention it in their paper. This means that they have either not read the book or that they are being disingenuous.
Their paper was also written so poorly that reading it felt like more of a slog than 600 pages by Piketty.