Hm, maybe it's called something else. I know that lemmy will default to post's language to "undetermined" if not manually set upon submission. This means if you disable it as a language option on your profile it won't show up. I'll try and get on kbin and see what the equivalent is. Because I have to go to the website in my browser to be able to reply to you. I'm sure apps will allow setting language on a per comment basis in the future but for now this is it.