emphasise need to ask for merge

Author: DavidSpickett

llvm/docs/Contributing.rst

@@ -114,12 +114,13 @@ other professional developers.
 After your PR is approved, ensure that:
 
   * The PR title and description describe the final changes. These will be used
-    as the title and message of the final squashed commit. The titles or
-    messages of any commits in the PR will **not** be used.
+    as the title and message of the final squashed commit. The titles and
+    messages of commits in the PR will **not** be used.
   * You have set a valid email address in your GitHub account, see :ref:`github-email-address`.
 
 Now you can merge your PR. If you do not have the ability to merge the PR, ask your
-reviewers to merge it on your behalf.
+reviewers to merge it on your behalf. You must do this explicitly, as reviewers'
+default assumption is that you are able to merge your own PR.
 
 For more information on LLVM's code-review process, please see
 :doc:`CodeReview`.