diff --git a/COLLABORATOR_GUIDE.md b/COLLABORATOR_GUIDE.md
index 2bab2e203145f0..5d0bfbfbb4339c 100644
--- a/COLLABORATOR_GUIDE.md
+++ b/COLLABORATOR_GUIDE.md
@@ -101,6 +101,8 @@ information regarding the change process:
 
 - A `Reviewed-By: Name <email>` line for yourself and any
   other Collaborators who have reviewed the change.
+  - Useful for @mentions / contact list if something goes wrong in the PR.
+  - Protects against the assumption that GitHub will be around forever.
 - A `PR-URL:` line that references the *full* GitHub URL of the original
   pull request being merged so it's easy to trace a commit back to the
   conversation that led up to that change.
diff --git a/doc/onboarding.md b/doc/onboarding.md
index e9d6a4bd244b9e..e22c876893fb20 100644
--- a/doc/onboarding.md
+++ b/doc/onboarding.md
@@ -164,8 +164,15 @@ onboarding session.
 
 ## Landing PRs: Details
 
-* Please never use GitHub's green "Merge Pull Request" button.
+* Please never use GitHub's green ["Merge Pull Request"](https://help.github.com/articles/merging-a-pull-request/#merging-a-pull-request-using-the-github-web-interface) button.
   * If you do, please force-push removing the merge.
+  * Reasons for not using the web interface button:
+    * The merge method will add an unnecessary merge commit.
+    * The rebase & merge method adds metadata to the commit title.
+    * The rebase method changes the author.
+    * The squash & merge method has been known to add metadata to the commit title.
+    * If more than one author has contributed to the PR, only the latest author will be considered during the squashing.
+
 
 Update your `master` branch (or whichever branch you are landing on, almost always `master`)