I was just showing someone the group inbox. They shared their screen and I was looking at the same group inbox view separately on my screen. They archived a message and, as expected, were returned to the group inbox where the message they just archived was gone. On my screen I expected the message to disappear as well but it did not. I had to click away and return to the inbox to see the updated message list without the moved message.
I suspect the same thing happens when someone deletes a message etc.
I’m not quite sure what the practical implications of this are and if it’s going to present any real problems. But I wanted to let you know for whenever group messaging gets some love and attention from the discourse team.