First of all, this is not a professional setting, he's not an employee there, and that forum is open for everyone.

Secondly, and way more important, people do that daily and no one cares especially when introducing oneself it's common to mention stuff like your wife/husband and your preferred pronouns, hell, my corporate slack profile has my pronouns and those of everyone else. I've worked with trans people who introduced themselves as trans on the first day, and no one cared. So no, it's perfectly okay for people to talk about themselves during an introduction even in professional settings.

Last but not least, people being uncomfortable is not a good reason to ban something, members of the KKK might be uncomfortable about working next to a black person, so what? Should the black person hide that he's black to not make the others uncomfortable? That's bullshit. If a person is uncomfortable by another one saying they're queer, then that first person needs to deal with it, being queer is part of who the other person is and he shouldn't have to hide who he is because someone might be uncomfortable about it. You mentioned religion, which I don't think falls into the same category because religion is a set of beliefs that many people change through their lives, but still, people wear crosses daily in professional settings and no one cares.