Fix #1053

docs/documentation/elements/button.html

@@ -539,7 +539,16 @@ variables:
 
     <div class="columns">
       <div class="column">
-        {{button_loading_example}}
+        <div class="block">
+          {{button_loading_example}}
+        </div>
+        <div class="message is-info">
+          <div class="message-body">
+            <p>
+              Since the loading spinner is implemented using the <code>:after</code> pseudo-element, it is not support by the <code>&lt;input type="submit"&gt;</code> element.
+            </p>
+          </div>
+        </div>
       </div>
       <div class="column">
         {% highlight html %}{{button_loading_example}}{% endhighlight %}