As I respond to this, your comment is outlined in a wide purple border. When I submit this response, I expect that your comment will no longer be outlined, but my comment will. If I refresh the screen, I expect neither of ours will.

This has been true since I started reading LW again recently, and I have mostly been paying no attention to it, figuring it was some kind of "current selection" indicator that wasn't working very well. But if it's an "unread comment" indicator, then it works a lot better.

Edit - I was close. When I submit, your comment is still purple, and mine isn't. If I refresh once, yours isn't and mine is. If I refresh again, neither is.