I'll just weigh in on this real quick -- I find it incredibly obnoxious when asterisks don't stay asterisks, because occasionally I just want some asterisks, damn it. BBcode is easy to remember by comparison for someone who isn't always dealing with Markdown, as well. I also would strongly object to moving to something just because everyone else is using it, because things don't necessarily get adopted because they're good -- it's often just because they're cheap, and I don't mean in terms of computing power.
Re: advantages of Discord -- centralization means convenience for the end user, at least in the short term. If you're willing to put up with excessive centralization, turning Discord into a hub for dealing with literally everything is easier than going between sites for various purposes, same reason as Facebook and Twitter are as huge as they are despite being hot garbage. In other words, it's probably easier to get people to use Discord because they don't have to leave Discord to do it. No replicating that with forum software.
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If the forum ends up relocating, it should move to an open source platform. Matrix is one that I would support. Fully FOSS, used by a lot of the open source community, federated, bridging with discord, etc. And if centralization is a good thing, 90% of matrix users are on matrix.org
We've already got a official Matrix channels bridged with the public parts of our Discord 'server' (although I can't remember if we've migrated them to the Matrix equivalent of a Discord 'server' as it predates that being a thing). Most of the organisational disadvantages of Discord apply equally to Matrix, though, as they've inherent features of chat, i.e. it's ephemeral stuff without loads of thought put into each post without a per-discussion index. We're having problems partially caused/exacerbated by these aspects, which wouldn't be the case if discussions happened on the forums, but discussions aren't happening on the forums, at least in part as most of the team sees them as more of a pain.