The default theme that comes with Mephisto, Simpla, doesn't include any article tags, even though Mephisto supports them through URLs. Tags can provide a clue to visitors of what the article is about, before reading it - and they can also improve the page ranking (for search engine optimization).

After checking the Mephisto documentation, I found the solution. Tags are available as an array article.tags, inside the articles for loop. Here is a sample code that displays the tags for the current article:

{% unless article.tags == empty %}
  <p class="articletags"><span class="taglabel">tags:</span> 
    {% for tag in article.tags %}{% unless forloop.first %}, {% endunless %}{{ tag | link_to_tag }}{% endfor %}
  </p>
{% endunless %}

There is also a list of all Mephisto variables available inside a Liquid template. Hope this helps, it took me some time to find this simple solution.