Hmm, subclasses are supposed to represent an IS-A relationship in my oldschool OOP books, typically a specialization of a more general (ie. abstract) outer class.   The multiple-inheritance case does make things a bit more sloppy, but then this problem has already been resolved by the BDFL via MRO, the same could probably apply with docstrings, with the user updating or using a blank docstring when that general rule doesn't work.

In any case, I found myself wanting this auto-inheritance for easier testing with doctest.  I don't want my subclasses to mess up invariants in my parent classes, and if the doctests were inherited this would be easy to check.

Just my (late) 2 cents worth after examining the current python issues list.