Where and how are escape quotes stripped when saving a taxonomy terms which include comas or quotes? in taxonomy_autocomplete:
https://api.drupal.org/api/drupal/modules!taxonomy!taxonomy.pages.inc/function/taxonomy_autocomplete/6 
we have the following code:

   // Commas and quotes in terms are special cases, so encode 'em.
      if (strpos($tag-&gt;name, ',') !== FALSE || strpos($tag-&gt;name, '"') !== FALSE) {
        $n = '"' . str_replace('"', '""', $tag-&gt;name) . '"';
      }


Imagine we have the taxonomy term which is exactly the following string:

George "madcow" Stewart


THe above code would cause the taxonomy autocomplete to display:

"George ""madcow"" Stewart"


I have re-implemented the taxonomy_autocomplete in order to work with a single term (no comma separated list of terms allowed). 
The problem now is that when we want to enter George "madcow" Stewart, a new term "George ""madcow"" Stewart"  is created, including all the extra quotes!

I cannot find where and how in core the escape quotes are stripped before insertion to the database&hellip;
Oh! I just found it:

The function taxonomy_node_save(&amp;$node, $terms) calls drupal_explode_tags()

https://api.drupal.org/api/drupal/includes!common.inc/function/drupal_explode_tags/6 

which has:

// If a user has escaped a term (to demonstrate that it is a group,
// or includes a comma or quote character), we remove the escape
// formatting so to save the term into the database as the user intends.
$tag = trim(str_replace('""', '"', preg_replace('/^"(.*)"$/', '\1', $tag)));