You're not missing anything content-wise if you play it solo. In solo mode you control all 4 of your party members during their turns, and in the multiplayer mode you control some of your party and your friend(s) control the others. The game content is the same but the experience is very different since multiple players are generally less tactically coordinated than a single person and they can wander the map separately
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