Put an S in the QR spoiler checkbox.

src/General/css/style.css

@@ -1407,7 +1407,7 @@ input#qr-filename {
 }
 
 /* Spoiler Checkbox, QR Icons */
-#qr-spoiler-label, #qr-filename-container > a {
+#qr-filename-container > label, #qr-filename-container > a {
   -webkit-flex: none;
   flex: none;
   margin: 0;
@@ -1419,9 +1419,26 @@ input#qr-filename {
 #file-n-submit:not(.custom-cooldown) #custom-cooldown-button {
   display: none;
 }
-#qr-file-spoiler {
+#qr-filename-container > label {
+  position: relative;
+}
+#qr-filename-container input[type="checkbox"] {
   margin: 0;
 }
+.checkbox-letter {
+  pointer-events: none;
+  position: absolute;
+  top: 2px;
+  left: 3px;
+  right: 3px;
+  text-align: center;
+  font-size: 11px;
+  font-weight: bold;
+  color: rgba(0,0,0,.6);
+}
+input[type="checkbox"]:checked ~ .checkbox-letter {
+  display: none;
+}
 #paste-area, #url-button, #custom-cooldown-button, #dump-button {
   opacity: 0.6;
 }

src/General/html/Features/QuickReply.html

@@ -30,6 +30,7 @@
       <input id="qr-filename" data-name="filename" spellcheck="false">
       <label id="qr-spoiler-label">
         <input type="checkbox" id="qr-file-spoiler" title="Spoiler image">
+        <span class="checkbox-letter">S</span>
       </label>
       <a href="javascript:;" id="qr-filerm" title="Remove file"><i class="fa fa-times-circle"></i></a>
       <a id="url-button" title="Post from url"><i class="fa fa-link"></i></a>