  We discuss the recently suggested Ricci-Gauss-Bonnet holographic dark energy
in Chern-Simons modified gravity. We have tested some general forms of the
scale factor $a(t)$, and used two physically reasonable forms which have been
proved to be consistent with observations. Both solutions predict a sign
flipping in the evolution of cosmic pressure which is positive during the
early-time deceleration and negative during the late-time acceleration. This
sign flipping in the evolution of cosmic pressure helps in explaining the
cosmic deceleration-acceleration transition, and it has appeared in other
cosmological models in different contexts. However, the current work shows a
pressure singularity which needs to be explained. The evolution of the equation
of state parameter $\omega(t)$ shows the same asymptotic behavior for both
solutions indicating a quintessence-dominated universe in the far future. We
also note that $\omega(t)$ goes to negative values (leaving the decelerating
dust-dominated era at $\omega=0$) at exactly the same time the pressure becomes
negative. Again, there is another singularity in the behavior of $\omega(t)$
which happens at the same cosmic time of the pressure singularity.
