They ban everyone who attempt to use a custom client?
I've been using Betterdiscord for years and have never been banned. Matrix looks good, but I don't think you're selling it well by throwing Discord under the bus without some very clear and obvious justification - nobody will be inclined to believe you.
Why doesn't Matrix just call "spaces" servers? By calling them spaces, they have created a learning curve for no reason.
Even just saying you have to download a client called Element to access Matrix is not intuitive. To access Discord, you download a client called Discord.