As with most of the cool features in tickers, this one was also feedback from a user. The user wanted to have simple way to distinguish between new and old messages. I usually scroll to the top, therefore I know that I read everything below, but every user is different.
Now when you enable the “Mark As Read” mode, you can mark a single message or all messages as read. This changes the background color of the selected messages and helps you to distinguish between new and old messages.
If you have a sane and useful feature request, too (not the ones that probably make a completely different app out of tickers) don’t be shy and contact me.