Been there with PVM, and we found aborting the "world" to be a bad thing.
I suggest "at most" just processes in COMM are aborted.
For MPI-1 picking either interpretation is OK
but looking ahead to MPI-2 with client servers
I wouldn't want a failed client to cause the server to be killed.
(this is what we ran into and had to fix in PVM)
Looking even further ahead (MPI-3?) if we incorporate some fault tolerance
then we don't want choices made in MPI-1 to hinder this work.
Al Geist