There were many many times when I was writing and sending PM messages when the member has left the chat long since. And you dont get a notification, you dont get a clear message that you're the only man left in the room so to speak. You have to scroll to the top and check the status in member is still participating. So what if you make this inside the PM conversation window to indicate changes to the conversation, like new member added, a member left and so on. Just like in topics.

Forgot to tag you guys @Jordan Invision @Matt 😄 as usual

I’ve made this a while back but it works well if there was only 2 users in the conversation or if everybody else left and now there’s only you:

Make it like a topic moderation “logs” between the posts will make it get lost too because you rarely read it all again; you usually go straight to the new post. Maybe make it more prominent in the current place, like with a red background in “user block” or something. 

This is actually great work @Adriano Faria