  In a recent review~Landsgesell et al., Soft Matter {\bf 15}, 1155 (2019)
stated that $\text{pH} - \text{pK}_a$ is a ``universal parameter" for titrating
systems. We show that this is not the case. This broken symmetry has important
implications for constant pH (cpH) simulations. In particular, we show that for
concentrated suspensions the error resulting from the use of cpH algorithm
described by Landsgesell et al. is very significant, even for suspension
containing 1:1 electrolyte. We show how to modify the cpH algorithm to account
for the grand-canonical nature of the cpH simulations and for the charge
neutrality requirement.
