Prova così (non testato)

Codice PHP:
<form name="formcomm" id="formcomm" >
<input name="idc" type="hidden" value="<?php print $idc; ?>">

<input name="utente" type="text" class="txtseach" id="utente" size="50" maxlength="250">

<textarea name="testo" cols="62" rows="7" class="textarearic" id="testo"></textarea>

<input name="button" type="button" class="BTseach" id="button" value="Inserisci commento" style="cursor:pointer" onclik="pagexmlinscomm();">