Hey, there’s no rule against speaking another language here! Just because you speak English doesn’t mean everyone else must do so.
Yes, most of the people here speak English, but so what? Let’s say you and your friends are out getting ice cream and everyone else gets vanilla. Does this mean you have to get vanilla? No. You’re free to get whatever flavor you want, users are free to speak whatever language they wish.
(Forgive the childish metaphor, but I think my point stands)
Some streams make you post in English but there’s no rule that everyone must comment in English.