strikethrough

inc/instance-config.php

@@ -326,3 +326,4 @@ $config['additional_javascript'][] = 'js/youtube.js';
 
 $config['markup'][] = array("/^\s*&lt;.*$/m", '<span class="orangeQuote">$0</span>');
 $config['markup'][] = array("/__(.+?)__/", "<span class=\"underline\">\$1</span>");
+$config['markup'][] = array("/~~(.+?)~~/", "<span class=\"strikethrough\">\$1</span>");

stylesheets/style.css

@@ -1959,6 +1959,10 @@ span.underline {
     text-decoration: underline;
 }
 
+span.strikethrough {
+    text-decoration: line-through;
+}
+
 span.orangeQuote {
     color: #FF8C00;
 }