Hi there,
I noticed an inconvenient case occuring while replying the messages:

Everytime I sent the message, the input area will be replaced by a notification of ‘message sent’, but then I cannot send another message in the same page, what’s more, if I directly refresh the page, it will ask me if I will resubmit the form again, which means I might send a duplicated message?
I think this situation is commonly seen when a user needs to send multiple messages to others, and it’s really inconvenient that I have to do the following steps to send a new message: 1.go back to the message list, 2.Locate the message thread with the user, 3. Click into the message detail and send a new message…

So I’m suggesting you to make the page show the input area after replying the messages, the notice of ‘message sent’ can be set to disappear after couple secs, or you can make the page automatically refresh itself, which is also a good way…