basically, the only advantage of this place is the ability to reply by email. Everything else that was listed in your comment can be done with Reddit, and Reddit suits this task better, because it is a mass of communities that can intersect with each other and share experience, it’s more popular, and has became a something like second stackwhatever.com for many people, because it is easier to use.
This hub is pretty much self-existing, and hard to be discovered, because it doesn’t mentioned anywhere but kakoune.com which looks like some fan-made site, not an official page. It should be mentioned in pinned post at r/kakoune, and at kakoune.org if you want more people to discover this place. But in my opinion, Reddit is more than enough to be hub for Kakoune users, and if it will be popular it would be able to show other people that community is strong. discuss.whatever.com doesn’t seem to be really popular, and usually more specific for developers community which isn’t a goal.
To summarize what I meant: the less popular community hub aggregator was chosen over one of the most popular community hub aggregator because of ability to reply by email.