Improve phrasing in "No surprise rebasing"

CONTRIBUTING.md

@@ -154,10 +154,10 @@ It's okay to rebase a branch if everyone using that branch is aware
 that rebasing might happen on that branch.  Otherwise, never rebase.
 
 In practice, this means that a developer doing iterative development
-on a branch (often as part of a review cycle) may rebase that branch
-with impunity, because their rebases won't affect anyone else: no one
-else is making changes on that branch, although some people might be
-watching and (re)reviewing a related merge request.
+on their own branch (often as part of a review cycle) may rebase that
+branch with impunity, because their rebases won't affect anyone else:
+no one else is making changes on that branch, although some people
+might be watching and (re)reviewing a related merge request.
 
 If multiple people are collaborating on a branch, then by default no
 one should rebase that branch unless the entire group agrees that