If you look at the data model `for object.__eq__` (https://docs.python.org/3.8/reference/datamodel.html#object.__eq__) you will see that it doesn't mention any actual implementation (unlike for __ne__). But https://github.com/python/cpython/blob/v3.8.3/Objects/typeobject.c#L3834-L3880 shows that object.__eq__ actually does have an implementation of `a is b`/`id(a) == id(b)`.

The word 'object' in this section is a bit confusing because it refers to any Python object, not to base class 'object' or an instance thereof.  I suspect that this usage predates the introduction of the latter in 2.2.

This interpretation is required for sentences like "By default, __ne__() delegates to __eq__() and inverts the result unless it is NotImplemented." and "If a class does not define an __eq__() method ..." (in the __hash__ entry) to make sense.  I think that the meaning of 'object' should be stipulated at the top of the section and mention the existence of base class 'object', and maybe list which of the following methods it has, and that they are inherited by subclasses.

The base class __eq__ implementation is implied in this paragraph in the __hash__ entry.

"User-defined classes have __eq__() and __hash__() methods by default; with them, all objects compare unequal (except with themselves) and x.__hash__() returns an appropriate value such that x == y implies both that x is y and hash(x) == hash(y)."

I think it worthwhile explaining that user classes get these defaults by inheriting them (and others) from 'object', and that the implication follows from inheriting a particular base class implementation of __eq__.  To put it another way, I believe the quoted paragraph makes the  definition a Python requirement rather than just a CPython implementation detail.

New changeset 3c69f0c933d4790855929f1fcd74e4a0fefb5d52 by Brett Cannon in branch 'master':
bpo-41910: specify the default implementations of object.__eq__ and object.__ne__ (GH-22874)
https://github.com/python/cpython/commit/3c69f0c933d4790855929f1fcd74e4a0fefb5d52

New changeset c3538b83816663d7b767391a375179a0ce923990 by Miss Skeleton (bot) in branch '3.9':
bpo-41910: specify the default implementations of object.__eq__ and object.__ne__ (GH-22874) (#22876)
https://github.com/python/cpython/commit/c3538b83816663d7b767391a375179a0ce923990

New changeset b2b3803081f07600710273b4f902b5be6e5596e7 by Miss Skeleton (bot) in branch '3.8':
bpo-41910: specify the default implementations of object.__eq__ and object.__ne__ (GH-22874) (#22877)
https://github.com/python/cpython/commit/b2b3803081f07600710273b4f902b5be6e5596e7

Brett, I presume you want this closed.

Thanks, Terry!

New changeset 4aa67853cc7d6ed4f9ebb726ceaa2c89f9feabda by Terry Jan Reedy in branch 'master':
 bpo-41910: move news entry  (GH-23695)
https://github.com/python/cpython/commit/4aa67853cc7d6ed4f9ebb726ceaa2c89f9feabda

New changeset b947b305a6833cc059214d5bdd2065edd65024c4 by Terry Jan Reedy in branch '3.8':
[3.8] bpo-41910: move news entry (GH-23698)
https://github.com/python/cpython/commit/b947b305a6833cc059214d5bdd2065edd65024c4

New changeset a3a4bf3b8dc79e4ec4f24f59bd1e9e2a75229112 by Terry Jan Reedy in branch '3.9':
[3.9] bpo-41910: move news entry (GH-23697)
https://github.com/python/cpython/commit/a3a4bf3b8dc79e4ec4f24f59bd1e9e2a75229112