As opposed to French, which famously exists as a natural truth of the universe. Even if we had never discovered French it would still be there... waiting.
I think the language analogy is actually very apt, because not every has to understand it, but the people you want to speak French with necessarily have to know it. Otherwise it just doesn’t fulfil any purpose.
Gender's an overloaded term. Are you talking about the internal feeling, the way someone's treated by others, the shared sense of a variable that differentiates people, social institutions, ideas, or something else?
Those of course are all related very strongly, but they're not the same thing. Different models of gender will define of differently, but that's usually just to best fit the area they're applicable to. If a philosopher tells you gender is a social construct, that's because they're analyzing things through the lens of social construction. Very useful, but merely one perspective.
I mean, I guess there’s a point to that, but isn’t there inevitably a social aspect to it? Especially in this post, where the person is saying others don’t have to understand it, meaning it’s clearly outwardly visible and part of who they are.
I’m not saying you should seek approval from anyone (for your gender nor anything else), because that’ll never happen. But denying the importance of some social acceptance for things in the social sphere is kind of weird, and feels like a “haha, unless…?” thing; you want others to understand and accept it, but the moment you don’t their acceptance becomes irrelevant and you never sought any acceptance at all. It feels like an unhealthy way to cope with rejection.