There is a huge wave of transitions from reddit/ forums towards discord because it offers voice chat / image uploads for free. It's not gonna last at that, chat is a bad format compared to hierarchical replies, hard to search etc. Gaming is their niche but at some point games will want to stop bleeding their community to them. There is also a proliferation of communities which leads to a lot of activity because it's a new platform, but as always, very few of them will survive. Then at some point they 'll also block all NSFW content and more people will leave. The value of their offering is that they re free, but money runs out, and slack already exists. Another case of overfunding for unsustainable growth.
I see it as complementary service. Reddit and forums aren't really suitable for chatting. Where as discord wills that niche very well. So communities will consist of forum/sub-reddit and a chat on Discord. One is more permanent and one is more ephemeral...
Reddit also provides image uploads for free, and most people on discord never use the voice chats as far as I can tell.
It's mostly real-time vs less than real-time communication. Discord for what is worth isn't that hard to search, and I wouldn't mind if they gave the option to some servers to have their logs automatically go to a crawlable page so they'd be indexed by Google. Of course, that won't work everywhere as real-time chats are often also used as they feel more ephemeral.
No one uses voice chat in public servers. You use voice chat in private friends servers. You get home turn on your desktop and see 3 friends on a chat and join in.
