odoo16/addons/portal_rating/views/portal_templates.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <template id="message_thread" inherit_id="portal.message_thread">
        <xpath expr="//div[@id='discussion']" position="attributes">
            <attribute name="t-att-data-display_rating">display_rating or False</attribute>
        </xpath>
    </template>
</odoo>