- where the conflict is not with the state of the resource, but with some other resource
- where the method allows multiple elements in a single request, but the client only included a single element
- where a single reason explains why none of the elements in the request could be satisfied
409: For example, the request tries to position the resource in an ordering before or after a resource that is not in the collection. So the conflict is with the state of the collection, not with the state of the resource identified by the request-URI. Or the request might try to position a resource in an unordered collection.
207: For example, on an ORDERPATCH where only a single change is requested, the behavior should be analogous with PROPPATCH where only a single change to a single property is requested -- must it be a 207?
For example, a PROPFIND or PROPPATCH on a dangling direct reference. Must the response be 207 (Multi-Status), or could it just be a 404 (Not Found)?