Hi Stewart,
I love your work. Happy anniversary for Q.js!
When run XHHH in your live editor, the results make sense to me. But the results you give are inconsistent with results of other simulators such as https://quantum-circuit.com/ and http://oreilly-qc.github.io/ Results from your live editor are grouped - yet results from the other simulators are interspersed.
Can you explain why these results are so inconsistent? Another library which returns results similar to yours for this example is https://github.com/adamisntdead/qics