Just click on it. It will show you who it is and what they said. You wouldn't have to respond to them.
This post was edited by Benedict Arnold at November 17, 2016 8:19 PM MST
There's a chat bubble that shows up at the top of the page, near the menu. If you press it, it opens the chat in a new tab. There's a gear at the top with the same options you see in the settings menu on a desktop.
This post was edited by Just Asking at November 17, 2016 12:13 PM MST