I prefer the Slack model where you can reply inside a thread and you replies stay within the thread instead of being scattered all over the place like IRC.
I hate to admit it, but this is one thing that Slack does better than IRC, except that in that model you do miss seeing everything that's talked about in the channel (because many of the conversations are hidden in the threads), but it's a better model for organization.
None of that changes its main societal flaw which is being a walled garden. So much loss of information.
Course, the bigger problem with centralized corporate services is that discord themselves could be shipping off that data on the backend to god knows who... but from the "protect me from other individual harassing me forever about shit I said once" front, Discord has some obvious appeal.
So I find that digging things up still happens (even a former employer did it to me!). I guess it feels more self-contained though, and it spreads a little slower.
Throwing back to the past, central logging is new, and twenty years ago it would've been hearsay where many people couldn't verify those claimed past conversations. I would have no issues with a two-month default expiry policy for these things.