Sergey Biryukov

In jQuery 1.5+ (bundled with WordPress 3.2+), AJAX requests on sites with IDN domains don’t work in IE or Opera.
On Edit Post screen, adding a new category results in JS error:
<pre><code>Message: 'parsed.responses' - is null or not an object
</code></pre>
On Categories screen, adding a new category silently fails.
According to <a href="http://bugs.jquery.com/ticket/8419#comment:3" rel="nofollow ugc">jaubourg’s comment</a> in jQuery bug tracker, the request is considered cross-domain and, since IE doesn’t support cross-domain requests, AJAX won’t find a suitable transport and bail out.
This plugin implements a workaround suggested there by making AJAX requests relative.
WordPress Trac ticket: <a href="https://core.trac.wordpress.org/ticket/18952" rel="nofollow ugc">#18952</a>

IDN AJAX Workaround

Fixes AJAX requests on sites with IDN domains in IE and Opera.

g30rg3x

Did you ever want to:
<ul>
<li>Have i15d/i18n permalinks?</li>
<li>Use non-ASCII characters on permalinks?</li>
<li>Personalize more your current permalinks?</li>
</ul>
i15d WP is a plugin specifically designed to fulfill this purposes without having to struggle. 
You just need to activate this plugin and it will be good-to-go. 
No modification to the core neither template files will be needed.

IDN AJAX Workaround vs i15d WP