That is the moderation check box, if you click that and say several other posts in the the thread, and then you go to the drop down moderation menu near the bottom right hand corner of the page, you can moderate the posts you have checked..........
This and a few dozen other reasons is why we are not ready for prime time, just yet, but I think we will be VERY soon.
Cheers!
PS, I'm still learning how to use this thing, and the bells and whistles in the ADMIN section are way more, like in a factor of 10 or so
But we are getting there guys!
Edit. Ok Playing with your post here. Just using edit, I am doing this.
Edit. Ok. I checked square box, post area is yellow. Same results.
Is checking the box supposed to give, have different results?