Strange. The screenshot above was made with ff 49, The raw HTML is below (double checked the raw output which is sent from the server to the browser):
<form>
<select id="uid" size="8" name="uid">
<optgroup label="villain">
<option value="122">Joe Dalton</option>
<option selected value="123">William Dalton</option>
<option value="124">Jack Dalton</option>
<option value="125">Averell Dalton</option>
</optgroup>
<optgroup label="cowboy">
<option value="126">Luky Luke</option>
</optgroup>
</select>
</form>
I see no chance, how the the equals and the quotes are inserted by the template above. Are you sure, you have no plugin etc. installed, that processes the results? try to check with wget, what the server sends back.
-gn