Well, as for many topics, also “privacy” in detail seems to be very different to many people. Personally I like the “auto-expire” feature in every messager app. But I also know people, who get angry about deleted chats. Because they forgot, what’s been said in the past or they want to look up stuff months ago, or … I else don’t know.
Hmm … are you talking about the original Signal app or the Molly app? Because I don’t really understand your news here.
For me, as far as I am aware, Signal has always been synchronising the chat history. The only condition being, that you have connected your device before in the past, which I think is a good privacy feature. (Although, I haven’t checked, how far back it goes. Never needed that.) - You don’t want any random new device read all our history, or do you?
Interesting feature, surely possible. I have seen that on “Threema”. Of course, secured by two layers of passwords/-phrases and strict connection procedure.