[Big Fred]

This is a trivial question but I'm just OCD enough to ask it:

Do any of you subscribe to various threads? If so, there is a page where you can go to peruse your subscribed threads and on the left-hand side of the viewing pane, there is sometimes a blue vertical line, sometimes not. There is also a legend at the bottom of the page which, I presume, is supposed to help one decode the colors, lines and other various indicators. (See photo below where the top few threads of my subscribed threads have a blue bar on the left hand side of the thread but the bottom two do not.)

Here's my (stupid) issue: I don't get what exactly the blue bar means. You would THINK it means that there are "New posts" in the tread based on the legend at the bottom of the page, but when I click on and look at the thread (and thus, I would think, make it so that any posts in it are no longer "new"), the blue line is still there.

Can anyone make a blue line on one of their subscribed threads either go away or appear? Maybe then someone could tell me how it works. Thanks.