I'm fine with removing my post (I was only providing info to the previous poster who had asked).
However, why do you feel like you're warranted in speaking for them?
I understand where you're coming from, but we've been freely talking about the ryona sakura forum, which is fairly similar in use to the discord, and they haven't complained (at least not yet) about ULMF users being on it, nor being on the discord itself. And they posted the link publicly on that sakura site anyway, so even if they DID want to keep it exclusive to Japanese-only, which they have not mentioned (yet), it's still an easily accessible public link.
As for the Discord itself, there are a LOT of gaijin already on it. Most of the users have English user names, and though I'm sure a good number of them are Japanese or can speak it given they can at least say hi, I'm also fairly sure that H-mugen editors like G-Bit, Hip-Ernov, and Lipcud are not. So far, it's been civil, and while my Japanese isn't great (yes, I translate Japanese games on this site, and no, my Japanese is still awful), nobody's said anything about Westerners invading their discord.
Point being that the Japanese seem more concerned about the plethora of people stealing their work and releasing it as their own, like Bison. I've strongly been against that and have ignored people (on this site) who have asked me to share their characters. But I don't know how it would be harmful to lurk and see what they're doing, just as we are on the ryona sakura site currently. Right now, the Discord is simply asking for civility and respect for that as defined in Japanese culture. I don't see how just observing their discussion would be offensive, especially since it's a valuable and rare resource into learning how to code H-mugen properly.