Dunno if you've seen it already but there's garnet.nostrian.net webui where Japanese discussion takes place. I don't quite know why but it seems like they use event kind 1 like forum posts. Their notes often appear to be referring to an ongoing conversation but never actually are in a thread. I see some of these come over my relays and love that Amethyst translates them.
Discussion
Actually I'm not at all sure that's what they're using. I'd just seen them discussing it once and assumed. I'm mostly describing posts I see in my global feed.