A few days ago the behaviour of NewsBlur changed for me. Before, stories were marked as read when scrolled past, but the behaviour had changed so that stories were marked read as soon as I selected a feed in the left-hand panel.
At the time I checked my settings and found that “Mark a story as read” was set to immediately (I didn’t manually change this so not sure how that happened). I changed the setting to “Manually by hitting u or m”. This solved the problem with stories being immediately read but they were not being read when scrolled past. I checked settings again and found “Mark stories read on scroll” was set to “Don’t automatically mark stories as read” (again not a change I had made), so I set it to “Mark stories as read when scrolled past”. However, changing this setting has no obvious effect, scrolling past a story in the main panel does not mark it as read.