validation suggestions

spec/Section 5 -- Validation.md

@@ -1873,7 +1873,7 @@ This is because {houseTrainedQueryTwoNotDefined} does not define a variable
 ${atOtherHomes} but that variable is used by {isHouseTrainedFragment} which is
 included in that operation.
 
-### All Operation Variables Used
+### All Variables Used
 
 **Formal Specification**
 
@@ -1882,6 +1882,11 @@ included in that operation.
   - Each {variable} in {variables} must be used at least once in either the
     operation scope itself or any fragment transitively referenced by that
     operation, excluding fragments that define the same name as an argument.
+- For every {fragment} in the document:
+  - Let {variables} be the variables defined by that {fragment}.
+  - Each {variable} in {variables} must be used at least once transitively
+    within the fragment's selection set excluding traversal of named fragment
+    spreads.
 
 **Explanatory Text**
 
@@ -1982,24 +1987,8 @@ fragment isHouseTrainedFragment on Dog {
 This document is not valid because {queryWithExtraVar} defines an extraneous
 variable.
 
-### All Fragment Variables Used
-
-**Formal Specification**
-
-- For every {fragment} in the document:
-  - Let {variables} be the variables defined by that {fragment}.
-  - Each {variable} in {variables} must be used at least once transitively
-    within the fragment's selection set excluding traversal of named fragment
-    spreads.
-
-**Explanatory Text**
-
-All variables defined by a fragment must be used in that same fragment. Because
-fragment-defined variables are scoped to the fragment they are defined on, if
-the fragment does not use the variable, then the variable definition is
-superfluous.
-
-For example, the following is invalid:
+Fragment variables must also be used within their definitions. For example, the
+following is invalid:
 
 ```graphql counter-example
 query queryWithFragmentArgUnused($atOtherHomes: Boolean) {