socialbase-1.1.0/templates/private_message/field--private-message-thread--members.html.twig

<div{{ attributes.addClass('message__thread-members') }}>
  <div{{ item.attributes.addClass('media media-middle') }}>
    {% for item in items %}
      {{ item.content }}{% if not loop.last %},{% endif %}
    {% endfor %}
  </div>
</div>