Adding a little note here to say, it seems like right click > ‘mark as read’ now doesn’t work. It did earlier when I first tested this fix, but now stories will only mark as read when using the keybind. Maybe that’s intended with the keybind setting only selected, but I’d consider the right click > ‘mark as read’ as separate from left-clicking a story 
Desktop again. Did download and use the mobile app briefly since I tested this bug earlier and it worked, in case that’s related!
(Edit: right click > ‘mark as unread’ does work, however)!