mocking and quoting bigots I've seen so far
:liberalism: turns to 
"you know it's hexbear when the tankie pronoun parade shows up to force pictures of pigshit in front of you!"* real quick
[*this is paraphrased, I can't remember the exact original quote]
Or "so suddenly I'm Hitler because i think people calling themselves Fae gender is dumb"
Or "why should i need to learn a new set of different pronouns for every person I meet?" (this followed two comments after "I'm literally not a transphobe, I work with plenty of trans colleagues who feel safe around me" (average lib being scratched in real time by having to acknowledge neopronouns))
.
All of these shitheads claimed to be allies when they started interacting but our brilliant pronoun tags immediately made them out themselves as the bigots they are who only pretend to be allies because it looks bad to be openly and proudly transphobic
TL;DR: 
That's really awesome. While I'm cis-(mostly)het, I'm close to several trans people in my life, some of whom have had significant struggles because of their gender. Hearing about such tools for self-exploration and acceptance is wonderful and you Hexbears continue to make my heart happy since federating.
It's such a simple tool and it does so much for people who want to explore their gender or who don't (yet) pass well enough to get gendered correctly or who basically never get gendered correctly because almost nobody just assumes you're enbie. It just instantly creates a space where everybody only knows you as your true self. I hope that other instances reach out to our devs and implement the tag system as well.