I long for this feature to be added too.

I second. I prefer marking read/unread by bolding and bg-color.
That's simple to do with Stylish for Firefox or for Chrome, I've made it for myself locally, the code is here: https://www.dropbox.com/s/ldy6tjjtincy8jf/restyle-theoldreader.css

I, too, had no idea there even was a read/unread marker until I read this.

This was a solved problem - Google Reader did it the right way.

The TOR way is significantly worse.

And having an indicator to display which post is currently read (between the read/not read state) would be helpful : if I stop my reading here, I'll know where I'll be the next time.

Actually, I know wich ones I have read, and wich ones aren't read, but I don't know if, when I'll close the window, I'll start on the not read or the next not read item.

Have to admit I was puzzled as to what indicated an item as read as I could see no difference between read/unread. The marker is so subtle, it was only when I read this wish-list item that I learnt about it.

Or perhaps the article titles should be bold for unread, regular / non-bold for read.

Yes the current marking for unread articles is a little too subtle.

Noticed the same, it's currently slower to see which feeds have unread items than in google reader for example.