anchor.diff:              unregistrations.Remove entityId |> ignore<bool>
   
           // register correlation
  -        if registered then
  +        if registered && not isolated then
               match ecs.Correlations.TryGetValue entityId with
               | (true, correlation) ->
                   correlation.Add this.Name |> ignore<bool>
  
positive.code: 
      member this.AddNode (parentIdOpt : Guid option) =
          let nodeId = Gen.id
          let system = SystemCorrelated<'c, 'w> (buffered, ecs)
          let addedOpt =
              match parentIdOpt with
              | Some parentId ->
  
negative.code:                 true
              | (false, _) -> false
  
          // unregister correlation from ecs if needed
          if unregistered && not isolated then
              match ecs.Correlations.TryGetValue entityId with
              | (true, correlation) ->
                  correlation.Remove this.Name |> ignore<bool>
  