Thanks to this Task:

T15401: Make the Remarkup Help Page Extensible

And thanks to the user speck, I discovered there are some cowsay-related binaries:

https://we.phorge.it/source/phorge/browse/master/externals/cowsay/

Permalink:

https://we.phorge.it/source/phorge/browse/master/externals/cowsay/;c705c8011e964945a6f73ae78087e188de0bd71f

Probably most of these are unused, because since 2015 Cowsay it's written in PHP and part of Arcanist:

https://secure.phabricator.com/rPc705c8011e964945a6f73ae78087e188de0bd71f

https://we.phorge.it/source/arcanist/browse/master/src/utils/PhutilCowsay.php

Why I think it's important to remove unused binary files:

• the ITSec team is less scared if they cannot find less legacy binaries around
• the embed team is more happy to save extra bytes from the working directory or phorge in production
• it seems that these things need to be updated with time to receive updates (e.g. security updates), but actually only the "cows" files need to be updated (just to have more)