anchor.diff:  * Two given instants `a` and `b` are equal if any only if they are of the same type and neither of them is _before_ or _after_ the other.
   
   
  -==== Durations ====
  +==== Durations
   
   * Two durations are equal if their components `months`, `days`, `seconds`, and `nanoseconds` are pairwise equal.
   * Durations are <<incomparable>> to any value including other durations, and can thus only be tested for equality.
  
positive.code: 
  
  [[orderability-def,orderability]]
  ==== Orderability ====
  
  [[global-sort-order,global sort order]]
  We propose that orderability be defined between any pair of values such that the result is always `true` or `false`.
  
negative.code: 
  
  [[conceptual-model]]
  === Summary of the conceptual model
  
  This proposal aims to simplify the conceptual model around equality, comparison, order, and grouping:
  
  