The one community that contributed most to convince me of Discourse is the Stay Forever community. Stay Forever is a German podcast about retro games, which, prior to the introduction of the Discourse forum, had discussions spread out over Patreon, Twitter and a Discord server. And while not everyone has moved over to the Discourse community, it has become my main point of interaction with other listeners (and the team). It’s also my point of reference for a clean Discourse theme (with great pixel art) and a good content structure for communities with not too much traffic.
Also, I like Meta 
Not only because there’s a lot of good info on Discourse here, but also because there’s a feeling of a vibrant community around the software.