I'm not sure that this is a valid feature request. As R. David Murray
has said, it's sort of an unwritten rule of ConfigParser-based
applications that they look for specific entries, but don't care what
else is there in the file - sort of in line with Postel's Law.

The appearance of multiple messages pretty much points to multiple
handlers handling the message; knowing the way the hierarchy works,
propagation should have been one of the first things to check (as I
assume you had added handlers both at and above [logger_Builder]. I know
hindsight is wonderful, and I'm sorry it took you 4 hours to find the
problem; but I'm not convinced by this that I need to put more error
checking into the fileConfig code.