Ping messages are system comments that appear after the task deadline is changed, or the task responsible person, observers and participants are changed. Ping messages help to keep track of the task and read all the latest updates on the task.
In the past, there were lots of system messages alongside employees' comments. There was pretty hard to understand what's going on.
Now, you can view the comments of employees involved in the task only. All the system messages are now hidden, but you can always view them by clicking the Show pings button.