I wouldnt call it a solution. It was supposed to help debugging the code.
Using ascii will slow down the code in parallel.
Probably, as it is related to xdmf with h5 encoding, it was adressed at https://bitbucket.org/fenics-project/dolfin/commits/6fbc9fb8e1272c4cdd73d7e2e432dc29ebfe03ac
and
backport xdmf+boost patch (#169) · conda-forge/fenics-feedstock@3ea2183 · GitHub