Discord is worse than Reddit for anything other than chatting. You can't view a Discord without an account, Discords aren't indexed by search engines or protected by google cache / archive.org, Discord's API usage policy is even more restrictive than Reddit's new one (it's completely against the TOS to create third party discord clients at all)...

Being able to look at the historical threads on a subreddit like hardwareswap is really important for learning the value of what you have. A format where every offer gets its own collapsible conversation thread is much better than every negotiator popping up in sequence.