EvilExecutor we thought about that, however we came in conclusion that not many people would actually use that. Discuss, GitHub and E-mail works the best for now (if someone is at Discuss, we can quickly respond and direct him to open a new discussion if it's not FF related, GitHub has really nice issues and pull requests system we use for extension requests and if someone doesn't have any of that or if they prefer a more private communication, they can contact us by E-mail).
We technically could create our own forum and Discord, but I don't think that many people would use it. As for the forum, there is not much unique to it IMO - people would use it to ask questions about Flarum, and not FreeFlarum since sometimes it is not clear that we are not affiliated with Flarum. We could have users request extensions there, but we can do that on GitHub too, so what's the difference... And that's pretty much all of what we could do with forum. I had idea about some events, such as forum showcases and such, but I don't think that many people would participate.
As for the Discord, I am very active there and I really like it, but it would not be very benefical for us or the community I think - yes, we could chat faster and more efficiently, share images, have many channels, but eventually it would grow inactive. I believe that it is better to not create many support and chat areas and stick with what we have for now. I am not saying that this won't change in the future, this is just my point of view.