It would be nice when the mark as read but is also visible when you scroll down you articles.
You can hit shift+a to mark as read. But I designed it the way it is today quite purposefully. I don’t know where the mark read button would go that it wouldn’t be in the way.
How about right next to the very large number of unread items at the top?
Alternatively, the title of the feed doesn’t need to scroll.
I agree with this wish, nice place for this button would be near the unread badge at the top or in the top right corner next to split or list view buttons.