the biggest issue with reddit/digg/hackernews style comments is how top comments can be gamed for profit. old forums had the problem of "first" and "bump" comments, but steering the conversation was harder.
Exactly. The "tree" part you can argue whether it's good or bad. The "upvote" part is universally bad. The fact that upvotes bump comments while downvotes will completely hide then... It's just terrible for discussion, and the reason reddit consistently devolves into echo chambers with everybody agreeing with everybody and piling on whoever doesn't.
Discord threads are just an addon on top of a chat. It's not really a real discussion. And the discord discussions (or whatever it is called) are again flat IIRC? Slack threads are flat. Both are chat platforms first and foremost I would say.
That said discord kinda does it and I just can't stand it. Unusable to me.