on page http://hl7.org/fhir/us/core/STU2/StructureDefinition-us-core-patient.html#quick-start
The second example seems to be missing a '|' between the system and code...

I think the problem is that you are putting the example in a markdown table, and thus the | character is seen as a column.

GET [base]/Patient/identifier=[system]|[code]

Support: Mandatory