odoo/ext/3rd-party-addons/invoice_comment_template/views/report_invoice.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

    <template id="report_invoice_document_comments"
      inherit_id="account.report_invoice_document" >
      <xpath expr="//div[contains(@class, 'page')]/table[1]" position="before">
        <p t-if="o.note1">
          <span t-field="o.note1"/>
        </p>
      </xpath>
      <xpath expr="//p[@t-if='o.comment']" position="after">
        <p t-if="o.note2">
          <span t-field="o.note2"/>
        </p>
      </xpath>
    </template>

</odoo>