Chatting someone that isn't available
When I try to chat w/someone in Skype that isn't at work, it'll tell me that they are unavailable. It says, [name of person] can't receive IMs right now. Status is unavailable or offline.
Teams doesn't seem to tell you anyone's status reliably.
Sean Ellis commented
Skype will indicate that they are offline but still allow you to send messages so that they can see them when they return. For people who are busy in meetings, it's essential that chat support this kind of asynchronous experience.