There's a worrying number of instances where people managing a foss project using taking their GitHub issue tracker, discussion boards, or some other public forum / discussion board and deciding to lock it and direct users to a discord guild because it's "easier". Or new communities that start up exclusively on discord but would be better served by alternatives.
Except it's not easier, there was an instance where a community had been using a discord channel as a file sharing platform for mods. An administrator was doing some housekeeping of the channels and accidentally deleted the entire chat history (which is easier to do than it sounds), and so irrevocably deleted all of the uploaded files, some of which were never recovered.
I'm pretty sure Digg, Facebook, Twitter, Tumblr, et. al. killed off classic forums. Discord and Slack and killed off IRC [though by and large, most will tell you that rumors of its demise is greatly exaggerated].
Depends on the server, and the channel on the server. Depending on the channel, you might get a handful of posts a week while the #general channel might be a non-stop firehose (at least on the more social Discords).
As to how it’s the closest alternative, mainly in that the atomic unit around which Discord is organized like Reddit is the community. On Reddit it’s subreddits and on Discord it is servers and it has gotten complex enough that for server owners Discord is slowly becoming a build your own social network toolbox.
Instead of the sidebar, each channel has pins. You can have an arbitrary number of channels for different topics, and you can even have forum channels where at the root level of the channel are forum topics. Once you’re in a server, searching it is trivial to see what people have said in Subject X in community Y, although this isn’t as good as say, searching all of Reddit is and you have to find a decent community to be able to search it.
Also a lot of subreddits are already running a Discord server on the side with the same or a similar mod team and have been for years. Doesn’t quite resolve Discord’s server discoverability issue, but Reddit doesn’t make the worst springboard for figuring out Discord either. If you support any Patreons or have similar memberships elsewhere, there’s a decent shot you already have access to a number of private members-only Discords which has kind of been my springboard into actually using my Discord account this past year.
But you know, it is very different. I don’t think it’s nearly as perfect an analogue to Reddit as Reddit was to Digg for Digg users, but it’s probably the closest to what Reddit already is.
Search is useless in a Discord server, especially one sufficiently busy enough. You cannot tell at a glance whether a keyword uttered at a specific moment in time is a crapshoot or not. You may have just a single person asking saying the word/phrase, or you may stumble upon whole conversations.
Threads are "ok" but still more ephemeral than a reddit thread.
I'm aware there are subs running discords on the side... and it's just on the side. I've had occasion to visit a few, and most of the time (from my own experience), they are just rehashing discussions already had on reddit and there is usually a channel or two that reposts links to reddit. It's great if you already spend the majority of time in Discord but I don't. I don't have time to sit in a discord and wait to have interesting discussions.
Earlier today, I was met with someone getting upset at me trying to have a discussion; editing prior comments because I called them out on something they had said [snide comments about people being asexual] and blocking me because "I don't fight on Discord".
All that said, I'm willing to give Discord a try here and there- but my prior experiences don't instill a huge amount of faith or hope in me. Until I find a Discord community that provides an analogue to normal discussion, which may never happen.
I can't imagine having to explain things to someone in real-time or helping them with programming issues. I imagine the vast majority of help channels cater to people coming off beginners' tutorials. Many of which can be covered with a simple search through Reddit or Stack Overflow.