I am having this issue as well. Chat came back for a brief moment out of nowhere and spammed my chat window with everything I had typed and everyone else had typed. As far as I can tell, no one received messages during this period.
I was able to confirm with a friend that she had not seen anything I had typed to her or even my logging status until that brief moment when the chat started working again.
Edit: I forgot to mention that is messes with the friends list as well. My friends list shows as blank when I open it during these communication outages.