Thanks for the report!

Everywhere.

Rather that this, it would be helpful to compile a list of inaccuracies.

As far as I know, we often use default None to mean unspecified. In the case of replace, specifying value=None is different from not specifying value at all. I don't see any instances where we have something like default <no_default>, which would perhaps be confusing. In my work, I've copied pandas' use of no_default but instead call it unspecified because of this reason.

@pandas-dev/pandas-core: any suggestions on how to document this better?

The sep argument of read_csv appears to be a more straightforward fix.

Conceptually these describe two different things - the signature shows the implementation whereas the docstrings describes the interface; while they usually align, that's not a hard requirement

Generally the no default sentinel is used when the value of None can be a legitimate argument (ex: wanting to actually fill an array with `None)

There are three things then: the signature, the docstring signature, the docstring full description. Sure I was talking about the docs part.

@rhshadrach , @WillAyd ,
let's synchronize.
Should be , default None added here?

Sure - feel free to push up any PRs for edits you see

Somewhat tangential:

Generally the no default sentinel is used when the value of None can be a legitimate argument (ex: wanting to actually fill an array with `None)

We currently use either None or no_default for an argument that can't appear in the signature of a function.
Wouldn't push hard here, but it seems better to me to only use no_default for this purpose.