Thank you all for your responses!

I’ve summarized them into the following 4 bullet points:

Discord is a poor replacement for Reddit. Here are 4 reasons why:

• Format: Discord’s main strength is chat-style messages, not forum-style discussion threads, like Reddit and Lemmy. Discord groups with more than a few dozen active users can quickly become disorganized.
• Barrier to entry: Content on Discord is inaccessible unless you have a Discord account, while almost all content on Reddit and Lemmy is available without registration.
• Discoverability: Google (and other search engines) index Reddit and Lemmy, and relevant threads show up in searches. Discord content cannot be indexed, and won’t show up in searches.
• Censorship: A Discord community is ultimately still controlled by a single Big Tech company, which can delete your community on a whim if they so choose. Lemmy, being a distributed social network, is inherently resistant to censorship.

Any further suggestions or tweaks?

I would use the argument that you can’t access content on Discord unless you have a discord account, on the other hand pretty much all content on Reddit (And Lemmy etc) is available without registration

Oh, and that it’s much more focused on chats than on forum-style posts

It’s more of a Slack alternative.

I feel like having to explain this means you don’t want to. Its chat.

Google indexes Reddit. Nobody can index Discord.

Discord has messages, not threads. It gets messy if you try to have multiple ongoing “threads” (just descord messages) at the same time.

And communities are easier to find and join than discord servers. (You can also lurk without joining.)

Most succinct? Messaging app vs Forum would do it it, imho.

Besides what others brought up already, another point is of course: No, a Discord community does not make you safe against your community being removed, ultimately, you still rely on their central service.

I mean, it’s a chat based app. It isn’t a forum based app/service.

It’s still an alternative because that just means it’s an option. It isn’t a good alternative, and it’s definitely not a replacement.

Whether it’s a good replacement for someone depends on what they’re looking for, there’s no answer that applies to everyone. And given that Reddit is such a cesspool, lots of things could qualify as better.