Add stern warning that nobody will read

changelog.d/607.change.rst

@@ -1,5 +1,5 @@
 ``attrs`` can now automatically detect your own implementations and infer ``init=False``, ``repr=False``, ``eq=False``, ``order=False``, and ``hash=False`` if you set ``@attr.s(auto_detect=True)``.
 ``attrs`` will ignore inherited methods.
-If the argument implies more than one methods (e.g. ``eq=True`` creates both ``__eq__`` and ``__ne__``), it's enough for *one* of them to exist and ``attrs`` will create *neither*.
+If the argument implies more than one method (e.g. ``eq=True`` creates both ``__eq__`` and ``__ne__``), it's enough for *one* of them to exist and ``attrs`` will create *neither*.
 
 This feature requires Python 3.

src/attr/_make.py

@@ -869,7 +869,17 @@ def attrs(
 
         So for example by implementing ``__eq__`` on a class yourself,
         ``attrs`` will deduce ``eq=False`` and won't create *neither*
-        ``__eq__`` *nor* ``__ne__``.
+        ``__eq__`` *nor* ``__ne__`` (but Python classes come with a sensible
+        ``__ne__`` by default, so it *should* be enough to only implement
+        ``__eq__`` in most cases).
+
+        .. warning::
+
+           If you prevent ``attrs`` from creating the ordering methods for you
+           (``order=False``, e.g. by implementing ``__le__``), it becomes
+           *your* responsibility to make sure its ordering is sound. The best
+           way is to use the `functools.total_ordering` decorator.
+
 
         Passing ``True`` or ``False`` to *init*, *repr*, *eq*, *order*,
         *cmp*, or *hash* overrides whatever *auto_detect* would determine.