Threads are an anti-feature to me. The only time I found them remotely useful is when I was doing an AI bot integration into the Matrix channel and it was just me and the bot.
I don't imagine using them much either even if they were feasible to use (I have the extra trouble of being primarily in a community that's bridged to discord, but the bridge doesn't bridge threads), but I've seen them used meaningfully in other discords for tangential/off-topic discussions.