diff --git a/doc/nep1.rst b/doc/nep1.rst
index d442651930..6924a86f6e 100644
--- a/doc/nep1.rst
+++ b/doc/nep1.rst
@@ -134,6 +134,18 @@ changed in the future.
   as what they are: Real words. So it's ``parseUrl`` rather than
   ``parseURL``, ``checkHttpHeader`` instead of ``checkHTTPHeader`` etc.
 
+- Operations like ``mitems`` or ``mpairs`` (or the now deprecated ``mget``)
+  that allow a *mutating view* into some data structure should start with an ``m``.
+- When both in-place mutation and 'returns transformed copy' are available the latter
+  is a past participle of the former:
+
+  - reverse and reversed in algorithm
+  - sort and sorted
+  - rotate and rotated
+
+- When the 'returns transformed copy' version already exists like ``strutils.replace``
+  an in-place version should get an ``-In`` suffix (``replaceIn`` for this example).
+
 
 Coding Conventions
 ------------------