It definitely was bound to that behavior in some version of OS X -- may have been even older, I think it changed around 2008 or 2009. I used the binding all th

It definitely was bound to that behavior in some version of OS X -- may have been even older, I think it changed around 2008 or 2009. I used the binding all the time in mail and safari until the default binding changed. And it drove me so crazy to lose the capability that I had to figure out the (incomplete) workaround. The left and right arrow keystrokes also always worked however require moving hands from keyboard and are less efficient to intersperse with other key strokes.