What about "if the target audience is known to not speak it" part do you not understand?

It's one thing to have your little community in whatever language and post there.

It's another to show up in a very much international community and start posting in whatever random language you want. Or, worse, start replying to comments written in English using your language. Like this guy. Just... How do you even do that? Aren't you supposed to kind of speak English to even understand the content of a comment you're replying to? Why not respond using it, then?

I'm not a native English speaker. My friends aren't either. Yet we all use it for pretty much the same reason. And if you think you can just chime in, go "你的母亲是只仓鼠,你父亲满身接骨木的气味", and be both perfectly understood and not downvoted, you're either a troll or an idiot.