That would really be an interesting concept, giving the community the ability to delete there accounts? Would be very helpful too, get rid of some peoples inactive accounts that they don't use anymore cluttering the system.
As interesting as a thing to have if I am not mistaken that type of thing could be placed under tutorials instead of a rule if I am understanding this correctly. Also I don't believe it would count as a rule too much, but I know a few other things that could be mentioned as a rule that could be added since some members of the community aren't too much aware of it being a rule. Though I believe that would be for another topic discussion.