account_voucher_comment/account_voucher_comment_view.xml

<?xml version="1.0"?>
<openerp>
    <data>
        <record id="account_voucher_comment_view" model="ir.ui.view">
            <field name="name">account.voucher.comment</field>
            <field name="model">account.voucher</field>
            <field name="inherit_id" ref="account_voucher.view_vendor_receipt_form"/>
            <field name="arch" type="xml">
                <field name="journal_id" position="after">
                    <field name="comment_obs" attrs="{'readonly':False}"/>
                </field>
            </field>
        </record>

        <record id="view_voucher_comment_tree" model="ir.ui.view">
             <field name="name">view_voucher_comment_tree</field>
             <field name="model">account.voucher</field>
             <field name="inherit_id" ref="account_voucher.view_voucher_tree"/>
             <field name="arch" type="xml">
                 <field name="reference" position="after">
                     <field name="comment_obs" string="Factura"></field>
                 </field>
             </field>
          </record>

           <record id="view_accountvoucher_comment_filter_search" model="ir.ui.view">
               <field name="name">accountvoucher.comment.filter.search</field>
               <field name="model">account.voucher</field>
               <field name="inherit_id" ref="account_voucher.view_voucher_filter_customer_pay" />
               <field name="arch" type="xml">
                 <search>
                     <field name="comment_obs" string="Factura"/>

                     <!-- <separator/>
                     <group string="Agrupar por">
                         <filter string="Cobrador Real" context="{'group_by':'employee_id2'}"/>
                     </group> -->
                  </search>
               </field>
           </record>
    </data>
</openerp>