Just a guess, from the codes at SpecialSetLabelDescriptionAliases.php

$intro = $this->msg(
	'wikibase-setlabeldescriptionaliases-introfull',
	$this->getEntityTitle( $entity->getId() )->getPrefixedText(),
	$languageName
);

• $1 is the page name (with prefix)
• $2 is the language name

One more thing, are you suggesting to add "GENDER" to this message only or all messages containing the word "you" or "your"?

Note that we have 5 very similar "...-introfull" messages.

Missing qqq docs are a bug and should be fixed, sure.

I'm not sure what gender support you expect and why. Currently the {{GENDER:...}} keyword occurs only once, in the message "wikibase-mylanguagefallbackchain-babel", and I'm not even sure if it's used right. "You" occurs 74 times in Wikibase messages. I don't think all of them should have a {{GENDER:...}} keyword. We need users that are able to speak a language where this is important and tell us which words in which messages need gender support. The best way to do this is to edit all our en.json (we currently have 3 for client/lib/repo) and submit that edit as a patch to Gerrit.

Change 197510 had a related patch set uploaded (by Lucie Kaffee):
Add missing qqq messages

https://gerrit.wikimedia.org/r/197510

Change 197510 merged by jenkins-bot:
Add missing qqq messages

https://gerrit.wikimedia.org/r/197510

The follow-up for the gender support is
https://phabricator.wikimedia.org/T93202