Recently I was setting up Twitch streaming on my PS4 for the first time in a long while. I could not get the streaming overlay (with comments on the side) to appear like it used to. I looked through all the relevant settings I could find.
Here's an example of the overlay I'm trying to get on my screen when I broadcast: http://snaps.vertigofx.com/044/snap_2016-11-02_08.58.24_783.png
I don't get any overlay. I only get the game full screen.
If you are trying to find out how to toggle whether comments are displayed or not, try this:
Under Advanced Settings (access by pressing the OPTIONS button):
Display Message to Spectators and Spectators' Comments
Select the checkbox to have messages to spectators and comments from spectators appear on screen. Comments appear only when your screen resolution is either 1080i or 1080p.
Additionally, from the PS4 Broadcasting Manual, it looks like this is how you get all comments to display, in case you want to see them all:
To view all comments, press the SHARE button and then select [Broadcast Settings] > [View Comments].
