By accident, I found out that jQuery appears to be removing the closing slash from a self-closing XHTML tag when inserting this tag through .append(), .prepend() and other ways, which results in invalid XHTML which - on its turn - results in mangled markup.

The following code, for example:

$('body').append('<input type="hidden" name="test" value="test" />');

Results in the following:

<input name="test" value="test" type="hidden">

Whilst the expected output is:

<input name="test" value="test" type="hidden" />

Please see the attached file for a working POC.