See microformats/mf2py#104. For backwards compatibility parsing, the Python parser changes the DOM on the fly. I believe the PHP parser does a similar thing. It turns out that – in the case of the Python parser – the same DOM object can’t be parsed successfully a second time. The microformats in the base document have been “damaged”.

How can we best test if this is the case with our parser too? Maybe also add a test case where we check that a second parse gives the same result?

Needs investigating. Thanks @kartikprabhu for bringing this up!

(This is basically a todo for myself, therefore also assigning myself.)