What you are describing here is microblogging like Twitter or Instagram, not using a chat to do chatting. Chatting, by design, is ephemeral and text only.

And yet that is how people use Discord - or more precisely, a mix of the two in the same interface. I think telling people they're not supposed to do something they find working is always losing battle.

This is actually a really good point and perspective. Couldn’t agree more.