DOC Add instructions about not removing anchors
@@ -751,8 +751,12 @@ In general have the following in mind:
* When editing reStructuredText (``.rst``) files, try to keep line length under
80 characters when possible (exceptions include links and tables).
-* Before submitting you pull request check if your modifications have introduced
- new sphinx warnings and try to fix them.
+* Do not modify sphinx labels as this would break existing cross references and
+ external links pointing to specific sections in the
+ scikit-learn documentation.
+
+* Before submitting your pull request check if your modifications have
+ introduced new sphinx warnings and try to fix them.
.. _generated_doc_CI:
