OP's home instance is hexbear, which asks users pronouns on signup and automatically adds them to your display name. Admins added it to stop accidental misgendering that comes with a lot of online people defaulting to he/him and to prevent singling out trans users with pronoun tags since it's required for everyone
there's like a 25 character limit (i think. it's 20 by default but it's changeable per instance by the admins) so if your name is short enough you can put it there.