social/mail_follower_custom_notification/views/mail_message_subtype.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <record id="view_mail_message_subtype_form" model="ir.ui.view">
            <field name="model">mail.message.subtype</field>
            <field name="inherit_id" ref="mail.view_mail_message_subtype_form" />
            <field name="arch" type="xml">
                <group position="inside">
                    <group string="Custom notifications">
                        <field name="custom_notification_mail" />
                        <field name="custom_notification_own" />
                        <field name="custom_notification_model_ids" attrs="{'invisible': [('res_model', '!=', False)]}" widget="many2many_tags" />
                    </group>
                </group>
            </field>
        </record>
    </data>
</openerp>