@jtsternberg
Actually, you are wrong.

You should never use context _x() function to describe placeholders. You should use only translator comments /* translators: %s: placeholder description */. The translator comment will appear on the sidebar:

As for the _x(), in WordPress core, we use context functions when a string is used in many places, but we want one of those strings to have a different meaning. When we add the context function, this string will appear as a separate string in translate.wordpress.org.

When using context function, It creates a new line in translate.wordpress.org, and allows you to provide a different meaning for this particular string.

Oh wow, well thank you very much for educating me! Looks like I've been using those functions improperly. I'll review this a bit more thoroughly when I get back to my computer, but should be good. Thanks again!

@jtsternberg the best example of proper use of _x would be:

_x( 'Buffalo', 'textdomain', 'A city in New York.' );
_x( 'Buffalo', 'textdomain', 'A large animal that lives in North America' );

Thanks for you contribution @ramiy!