Oh, I just noticed it seems this is a Qt only thing! A few minutes ago I compiled it against GTK2 and I cannot move the selection horizontally at all.
Win32 can also do that.
With some extra effort the similar functionality can be implemented on Cocoa.
But that certainly turns ListView into GridView. Where it's no longer a list of items, but rather a matrix of data.
Not a bad thing, if you ask me, but implementing on platforms without native support (i.e. Gtk2) might not be possible at all.
As an initial implemented, I'd recommend to create some sort of the class helper that the method like GetSelectedColum() or GetSelectedRect().