How do you comment out in Liquid?

In Liquid you comment out using the {% comment %} and {% endcomment %} tags:

{% comment %} This is a comment in Liquid {% endcomment %}

It doesn't matter if the comment is inline or a block comment.

{% comment %}
    This is a block comment in Liquid
{% endcomment %}

If, like me, you are looking for a solution that actually comments out "anything"/everything between the comment tags (as described in the documentation), you can use the {% raw %} tag (in conjuction with the {% comment %} tag if you don't want anything rendered in the browser), e.g.

{% comment %}
    {% raw %}
        Here is some text that I don't want displayed and
        {% some_liquid_stuff_that_I_don't_want_parsed %}
    {% endraw %}
{% endcomment %}

will render nothing at all, while

{% raw %}
    Here is some text that I want displayed but
    {% some_liquid_stuff_that_I_don't_want_parsed %}
{% endraw %}

will render

Here is some text that I want displayed but

{% some_liquid_stuff_that_I_don't_want_parsed %}

Additional information on this GitHub thread.