  Rastall gravity is the same as General Relativity, with a simple algebraic
redefinition of what is called the energy-momentum tensor. Despite it having
been very clearly explained by M. Visser several years go, there are still many
papers claiming big differences between the two formulations of gravitational
equations and trying to use them for problems of physics. When going this way,
the totally ignored task is to explain why the conserved energy-momentum
quantities and the quantities used for other purposes are different from each
other. Moreover, when researchers are using the non-conserved energy density
and pressure for determining the sound speed, it is just inconsistent with the
Rastall gravity. I carefully explain all this, and also show how one could
construct a variational principle for producing equations in the Rastall form.
