I can’t seem to do it through append.
Creating a reusable node library http://www.blendercookie.com/2009/07/16/creating-a-reusable-node-library/
If you select the node(s) you want to append and press Ctrl-G to create a group, you can then append the group into another scene.
You may prefer to link to the group rather than appending it, if you do intend for the node-group to become a reusable asset within your project … i.e. such that, if you need to make a global change you will need only change the one linked-to resource.
If the resource is “appended,” it is by definition “duplicated.”