I have to say that their monetisation so far has been excellent, at least from my point of view.

I don't believe they have paywalled any core features, only paywalled a few new features that are cosmetic only. If you don't pay for Discord Nitro or anything, you can still chat, call, join and use servers. The biggest advantage of Nitro is actually shared with everyone on your favorite server, and by 'boosting' the server you give features to everyone on it. I like that.

Is there any way that they could have monetised it better? I see it as pretty creative and user-friendly, given there's not many avenues to monetise a free service such as a chat.