Chat works better than forums.
Speaking as a library maintainer, I've got GitHub issue that stayed there for months before I replied. That's because my time as a contributor is very limited and I get fatigue when replying to too many support tickets.
And you'd think, oh wait but there are other people willing to reply. But not really. Forum, email groups, even StackOverflow only work when the projects you're talking about are insanely popular.
This is because of two reasons:
1. people with problems are bad at describing those problems — this is why StackOverflow answers often don't answer the freaking question, but rather try to guess what the author wanted, a trend that's driving me insane, because I often want the answer to the question being asked and not something else; whereas on a chat channel, people have conversations, which helps clarify the intent
2. people are afraid of being wrong; but chat is more casual, so in my experience more people end up participating
Chat has other benefits. You can have off topic conversations, you can make jokes, you can make friends. I do wish Gitter had threaded conversations. They promised it at some point but nothing came of it.
Also, I do like Discourse (https://discourse.org). It does a good job to mix some chat features with forums. Scala has Discourse forums, like for example https://users.scala-lang.org ... but the Scala Gitter channel is way more popular.
And one final thought: I know communities that have virtually no meaningful online presence. You might be annoyed at our choice for using Gitter, but at least you've got some chat channels to go to.
