I think the author makes a good point here. But I also think a comment can serve as an invitation for a new test case (i.e. Bugfix comments as he describes them).
PEP8 also says "The naming conventions of Python's library are a bit of a mess, so we'll never get this completely consistent -- nevertheless, here are the currently recommended naming standards. New modules and packages (including third party frameworks) should be written to these standards, but where an existing library has a different style, internal consistency is preferred."