> That sort currently uses __lt__ only is, in my opinion, an implementation detail.

Its only an implementation detail until the language specification defines it as a guarantee of the language. Then it becomes part of the sorting API.

Personally, I think it is a nice feature that sorting works for objects which define only __lt__, and it sounds like Tim is happy for that to be part of the sort API.

This is documented under list.sort() but not sorted():

https://docs.python.org/3/library/stdtypes.html#list.sort

https://docs.python.org/3/library/functions.html#sorted

Rather than removing it from the HOWTO, I would rather document that fact under sorted() as well.

If you still want to argue that we should not document this as a language guarantee, for the sake of other implementations such as Jython and IronPython, you should raise it on Python-Dev. It would probably help if you had other implementation maintainers state that this was a burden on them.

For what it is worth, it seems that Jython 2.5 supports this feature too.