> Relatedly, having a long term archival might come as a bit creepy, even. In apps this happens too, but at least I can say something extremely controversial and delete it for both people a couple minutes later. Or send a "view once" mesage.
I agree but in practice Facebook Messenger, WhatsApp etc are quite long term already. I can easily look up my chats from 15+ years ago on Fb.
But there is indeed a cultural unease, and it relates to the other top h post about social cooling. As you said, people want an online equivalent of phone calls and in person discussion. It's creepy and in some places even illegal to record phone calls or live conversations.
On the other hand, written letters used to be private but meant for archival. Many people inherit a big box of neatly organized letters received from friends and family when grandma etc die.
Email is a bit more letter-like in this.
But these norms are in flux and especially for different generations the intuition can be different.