Not working well for me. I keep getting an error that messenger is unavailable and there is not a 'mark as read' button anywhere. It also blocked messages from my friend that I was talking to in the small chat window. I had to go to the full page 'see all in messenger' to see her message.
I like this addon very much :-D but I would like very much to have an option thanks to which when I turn it off I will see that the other person has read this message which I sent and how I turn it so that I will not see if the other person has read it or not and this applies to my friends who will send me a message :-)