this interface is just about the most pointless code in all of PM or Bukkit. In over 4 million lines of code on Poggit, a Google search and a GitHub search, I didn't find a single usage of it that wasn't just bukkit internals code copy pasta, a spoon, a port of PM/Bukkit/whatever into a different language, or someone's generated javadoc.
this makes PermissionAttachment more and more like Permission, except that it doesn't have a name.
Right now, the only value of this API change is that it allows breaking references to dead Permissibles, but in the future it should be possible to reuse a single PermissionAttachment on multiple Permissibles.
