  Oliinychenko, Bugaev and Sorin [arXiv:1204.0103 [hep-ph]] considered the role
of conservation laws in discussing possible weaknesses of thermal models which
are utilized in describing the hadron multiplicities measured in central
nucleus-nucleus collisions. They argued to analyse the criteria for chemical
freeze-out and to conclude that none of them were robust. Based on this, they
suggested a new chemical freeze-out criterion. They assigned to the entropy per
hadron the ad hoc value 7.18 and supposed to remain unchanged over the whole
range of the baryo-chemical potentials. Due to unawareness of recent
literature, the constant entropy per hadron has been discussed in Ref. [Fizika
B18 (2009) 141-150, Europhys.Lett. 75 (2006) 420]. Furthermore, it has been
shown that the constant entropy per hadron is equivalent to constant entropy
normalized to cubic temperature, an earlier criterion for the chemical
freeze-out introduced in Ref. [Europhys.Lett. 75 (2006) 420, Nucl.Phys.A764
(2006) 387-392]. In this comment, we list out the ignored literature, compare
between the entropy-number density ratio and two criteria of averaged energy
per averaged particle number and constant entropy per cubic temperature. All
these criteria are confronted to the experimental results. The physics of
constant entropy per number density is elaborated. It is concluded that this
ratio can't remain constant, especially at large chemical potential related to
AGS and SIS energies.
