At the time Signal didn't have the swipe-right-to-reply behaviour, nor the ability to lock audio message recording so you can record handsfree. But it has both

At the time Signal didn't have the swipe-right-to-reply behaviour, nor the ability to lock audio message recording so you can record handsfree. But it has both now! As far as I know yes Whatsapp uses some of Signal's tech but doesn't implement it in exactly the same way.