Vertical grey bars on the left of conversations

I am seeing this from the starting of using the Microsoft Tech Community. There are vertical grey bars on the left of conversations on the Main screen of Microsoft Tech Community and its communities. I see that they are on some posts only and they turn purple when that post is marked as the best response. I wanted to know that if they mean something in the Microsoft Tech Community.Grey Bars appearing on some posts on the main screen of Microsoft Tech Community.