I agree with what you said mostly. I wonder though if the message could be clearer in the docs. I remember that the rule about the module being importable without side-effects, but didn't even consider that for the interactive session.

If I understand your analysis correctly, you're basically saying that "don't use multiprocessing" could be a general rule for interactive interpreters? Which would also affect any ipython session like ipython notebooks? (seems to be confirmed if you google for "multiprocessing ipython crash"...) If that's true, maybe that specific case should be spelled out in the docs more explicitly.