It's always been possible to remove focus from all selected files in Finder by pressing the ⎋ Escape key. It would appear that this is no longer possible in OS X Mavericks. I navigate the Finder entirely via keyboard and using ⎋ Escape is something I do quite frequently.
I've looked at nearly every preference pane I could think of as well as the contents of
com.apple.universalaccess.plist, but no luck so far (or I'm just not seeing it).