  Puzzled by the indication of a new critical theory for the spin-1/2
Heisenberg model with a spatially staggered anisotropy on the square lattice as
suggested in \cite{Wenzel08}, we study a similar anisotropic spin-1/2
Heisenberg model on the honeycomb lattice. The critical point where the phase
transition occurs due to the dimerization as well as the critical exponent
$\nu$ are analyzed in great detail. Remarkly, using most of the available data
points in conjunction with the expected finite-size scaling ansatz with a
sub-leading correction indeed leads to a consistent $\nu = 0.691(2)$ with that
calculated in \cite{Wenzel08}. However by using the data with large number of
spins $N$, we obtain $\nu = 0.707(6)$ which agrees with the most accurate Monte
Carlo O(3) value $\nu = 0.7112(5)$ as well.
