plone.app.discussion/plone/app/discussion/permissions.zcml

<configure
    xmlns="http://namespaces.zope.org/zope"
    i18n_domain="plone">

    <!-- custom permissions are defined here -->

    <permission
        id="plone.app.discussion.ViewComments"
        title="View comments"
        />

    <permission
        id="plone.app.discussion.ReviewComments"
        title="Review comments"
        />

    <permission
        id="plone.app.discussion.EditComments"
        title="Edit comments"
        />

    <permission
        id="plone.app.discussion.DeleteOwnComments"
        title="Delete own comments"
        />

    <permission
        id="plone.app.discussion.DeleteComments"
        title="Delete comments"
        />

</configure>