Sometimes I read an article and wish to mark it in some way, so that I can come back to it later and read it again.

Right now, the only way to do anything remotely like this is to "watch" the thread.

It would be much more useful if there was an easy way to flag an article with some kind of icon (perhaps in its own column in the header pane, to make it easily findable) and/or with a user-selectable color(s).

Of course, unflagging an article should be just as easy.

Perhaps there could be a "Flag article" item in the context menu that's brought up when the user right-clicks on the article in the header pane.