Improve comments.

config/nginx.conf

@@ -157,15 +157,20 @@ http {
  
         # Strip asset tags
         location ~ ^/(images|javascripts|openlayers|stylesheets|user/image)/ {
+            # Strip asset tags
             rewrite ^/(.*)/[0-9]+$ /$1;
+
+            # Set expiry to the maximum - the asset tag will change
+            # when there is a new version
             expires max;
 
-            # Handle Special Case Expiry
+            # Only cache OpenLayers for seven days though
             if ($uri ~ ^/openlayers/) {
                 expires 7d;
             }
         }
-        # Handle Special Case Expiry
+
+        # Cache the embedded map page for seven days
         location ~ ^/export/embed.html$ {
             expires 7d;
         }