DOCS-841 add examples for usePowerOf2Sizes, remove random double quote

Author: Ed Costello

source/reference/command/collMod.txt

@@ -15,11 +15,11 @@ collMod
 
    .. code-block:: javascript
 
-      db.runCommand( {"collMod" : [collection] , "[flag]" : [value]" } )
+      db.runCommand( {"collMod" : [collection] , "[flag]" : [value] } )
 
-   In this command substitute ``[collection]`` with the name of the
-   collection, and ``[flag]`` and ``[value]`` with the flag and value
-   you want to set.
+   In this command substitute ``[collection]`` with the name of a
+   collection in the current database, and ``[flag]`` and ``[value]``
+   with the flag and value you want to set.
 
    .. index:: document; space allocation
    .. index:: usePowerOf2Sizes
@@ -38,6 +38,21 @@ collMod
       will be inserting and deleting large numbers of documents to
       ensure that MongoDB will effectively use space on disk.
 
+      .. example::
+
+         Enable :collflag:`usePowerOf2Sizes` on the collection `sensor_readings`:
+
+         .. code-block:: javascript
+
+            db.runCommand({collMod: "sensor_readings", usePowerOf2Sizes:true })
+
+         Disable :collflag:`usePowerOf2Sizes` on the collection `products`:
+
+         .. code-block:: javascript
+
+            db.runCommand( { collMod: "products", "usePowerOf2Sizes": false })
+
+
       .. note::
          .. versionchanged:: 2.2.1
             If you're using :collflag:`usePowerOf2Sizes`, ensure
@@ -51,6 +66,6 @@ collMod
 
          .. Commenting out the following after DOCS-717, it does take
             a lock but its to cover a very small metadata change.
-            
+
             This command obtains a write lock on the affected database
             and will block other operations until it has completed.