Comment on "Black Hole Entropy: A Closer Look".

In a recent paper (Entropy 2020, 22(1), 17), Tsallis states that entropy-as in Shannon or Kullback-Leiber's definitions-is inadequate to interpret black hole entropy and suggests that a new non-additive functional should take the role of entropy. Here we counterargue by explaining the important distinction between the properties of extensivity and additivity; the latter is fundamental for entropy, while the former is a property of particular thermodynamical systems that is not expected for black holes. We also point out other debatable statements in his analysis of black hole entropy.