In Czech, translation of word "mentor" should differ by mentor's gender. For that purpose, I need a parameter containing mentor's username, so I can use it with GENDER. Temporarily overrode TWN's translate with https://cs.wikipedia.org/w/index.php?diff=17317219.
Other messages like Growthexperiments-homepage-mentorship-intro already contains mentor's username, and I don't see why this shouldn't.