In another sense, if we mandate specific symbols for mpif.h/use mpi, we might break some tools, but put ourselves in a better place for the future.  Since a tool already has to sense which back-end symbol to use mpif.h/use mpi (lower case, caps, 1 underscore, 2 underscores -- none of which are mandated by the Fortran spec, by the way; it's just common convention), is it really a hardship to add another symbol name to check during the tools configuration/building mechanism?

I am more worrying about existing tools - those would all
have to be changed.

Martin