View difference between Paste ID: 8zPd9JN4 and akkXcGtv

 // ABBC Live Compiler for http://dis.4chan.org/
 // by Tablecat <http://tablecat.co.cc>
 
 var init = function() {
     var forms = document.forms;
     for (var i = 0; i < forms.length; i++) {
         if (forms[i].action === 'http://dis.4chan.org/derefer') continue;
         var preview = document.createElement('div');
         preview.className = 'preview';
         preview.style.display = 'none';
         forms[i].appendChild(preview);
         var textarea = forms[i].getElementsByTagName('textarea')[0];
         textarea.onchange = textarea.onkeyup = function() {
             var comment = this.value;
             var thread = this.parentNode.parentNode.parentNode.parentNode.parentNode.id.value;
             var script = window.location.href.replace(/^http:\/\/dis\.4chan\.org\/([^\.]+)/, '$1');
             comment = markup(clean_string(comment), thread, script)[0];
             this.parentNode.parentNode.parentNode.parentNode.parentNode.lastChild.style.display = comment ? 'inline-block' : 'none';
             this.parentNode.parentNode.parentNode.parentNode.parentNode.lastChild.innerHTML = comment;
         }
     }
 };
 
 var clean_string = function(str) {
     str = str.replace(/[\x00-\x08\x0B-\x1F\x7F]/g, "");
     str = str.replace(/^(\n|\x20)+|[\s]+$/g, "");
     str = str.replace(/&/g, "&amp;");
     str = str.replace(/</g, "&lt;");
     str = str.replace(/>/g, "&gt;");
     str = str.replace(/\"/g, "&quot;");
     return str;
 };
 
 var markup = function(str, thread, script) {
     var tagList = [ "#" , "code" , "b" , "i" , "o" , "u" , "s" , "aa" , "m" , "spoiler" , "sup" , "sub" ];
     var malformed = 0;
     var quoteRe = /&gt;&gt;([0-9\-\,l]+)/g;
     str = str.replace(quoteRe, '<a href="read/'+script+thread+'/$1">&gt;&gt;$1</a>');
-    // super tags
+    // escape & code tags
     for (var i = 0; i < tagList.length; i++) {
         var tag = tagList[i],
         re = new RegExp("(^|[\\s\\S]*?)\\["+tag+"\\]([\\s\\S]*?)\\[\\/"+tag+"\\]($|[\\s\\S]*)", "g");
         while ( str.match(re) ) {
             if (tag === "#")
                 str = str.replace(re, "$1"+escape_tag(RegExp.$2)+"$3");
             else if (tag === "code")
                 str = str.replace(re, "$1<code>"+escape_tag(RegExp.$2)+"</code>$3");
             else
                 break;
         }
     }
     // quote
     var pattern = new RegExp("(\\n|^)&gt; (.*?)(\\n|$)", "g");
     while ( str.match(pattern) )
         str = str.replace(pattern, "$1<span class=\"quote\">$2</span>$3");
-    // regular tags
+    // other tags
     for (var i = 0; i < tagList.length; i++) {
         var tag = tagList[i],
             re = new RegExp("(^|[\\s\\S]*)\\["+tag+"\\]([\\s\\S]*?)\\[/"+tag+"\\]($|[\\s\\S]*)", "g");
         while ( str.match(re) ) {
             var before = str.replace(re, "$1"),
             content = str.replace(re, "$2"),
             after = str.replace(re, "$3");
             if (fail_check(content, tagList)) {
                 str = before + "\x1FB"+tag+"\x1FC" + escape_tag(content) + "\x1FB/"+tag+"\x1FC" + after;
                 malformed++;
             }
             else if (tag.match("^(b|i|s|u|sup|sub)$"))
                 str = before + '<' + tag + '>' + content + '</' + tag + '>' + after;
             else if (tag === "m")
                 str = before + '<tt>' + content + '</tt>' + after;
             else if (tag === "rem")
                 str = before + after;
             else if (tag.match("^(spoiler|aa|o)$"))
                 str = before + '<span class="' + tag + '">' + content + '</span>' + after;
             else
                 break;
         }
     }
     str = str.replace(/\n/g, "<br>");
     str = '<blockquote style="border:1px dashed #000;padding:0.5em;background:#EFEFEF">'+str+'</blockquote>';
     //if (malformed > 0) str += '<div style="color:red"><b>Warning: Malformed markup, '+malformed+' error(s)</b></div>';
     return [unescape_tag(str), malformed];
 };
 
 var escape_tag = function(str) {
     str = str.replace(/&gt;/g, "\x1FA");
     str = str.replace(/\[/g, "\x1FB");
     str = str.replace(/\]/g, "\x1FC");
     return str;
 };
 
 var unescape_tag = function(str) {
     str = str.replace(/\x1FA/g, "&gt;");
     str = str.replace(/\x1FB/g, "[");
     str = str.replace(/\x1FC/g, "]");
     return str;
 };
 
 var fail_check = function(str, tagList) {
     for (var i = 0; i < tagList.length; i++) {
         var tag = tagList[i],
             reup = new RegExp("(.*)\\["+tag+"\\](.*)","g"),
             redwn = new RegExp("(.*)\\[/"+tag+"\\](.*)","g"),
             count = 0;
         while ( str.match(reup) ) {
             str = str.replace(reup, "$1$2");
             count++;
         }
         while ( str.match(redwn) ) {
             str = str.replace(redwn, "$1$2");
             count--;
         }
         if (count !== 0) return true;
     }
     return false;
 };
 
 if (window.location.href.search('^http://dis.4chan.org/[^\.]+') != -1) {
     window.onload = function() { init(); };
 }