>> Why are __flags__, __basicsize__, __itemsize__, 
>>__dictoffset__, and __weakrefoffset__ interesting?
>
> I haven't said they are, but on the other hand I don't see 
> why consistency is a bad thing.

IMO, they're not interesting because they're not documented attributes in Python's data model. They don't exist in other implementations, such as PyPy. So I'd prefer to hide them and, as much as possible, discourage developers from thinking it's okay to use them. They may be interesting attributes while developing extension modules that define new types, but anyone working at that level surely doesn't need the help of dir() to know what attributes are available.