{% macro translations_for(article) %}
{% if article.translations %}
<p id="list-of-translations">
This post is also available in:
    {% for translation in article.translations %}
    <a href="{{ SITEURL }}/{{ translation.url }}">{{ translation.lang }}</a>{%if not loop.last %}, {% else %}.{% endif %}
    {% endfor %}
</p>
{% endif %}
{% endmacro %}

{% macro translations_for(article) %}
{% if article.translations %}
<p id="list-of-translations">
This post is also available in:
    {% for translation in article.translations %}
    <a href="{{ SITEURL }}/{{ translation.url }}">{{ translation.lang }}</a>{% if loop.index0 + 2 == loop.length %} and{% elif not loop.last %}, {% endif %}
    {% endfor %}
</p>
{% endif %}
{% endmacro %}

Add "and" before the last item in the translation and remove full stop after the last item
Add "and" before the last item in the translation and remove full stop after the last item
