I guess we have a different view of what to expect from the method ;-) What i'm actually looking for is a insert_after/before like method. This comes of course from how we use the lib:
We use sortifiable for ordering pages in a CMS, with a drag and drop interface that basically moves a node 'the left/before of a target node'. I would expect to be able to do that somehow without having to check the internal state of the list.