My main concern is that the door not be closed on improving the user experience relating to this behaviour of the compiler.

This issue was raised as a bug for the compiler (which is C-coded). I'd be very happy for this issue to be closed as 'not a bug' for the compiler, provided the door is left open for Python-coded improvements for the user experience. 

I suggest that the issue title be changed to: The two-pass compile(bad_src, ...) sometimes does not report first error in bad_src

These two changes to the details of closure would be sufficient to meet my concern. I hope they can be accepted.

By the way, I see these improvements being done as a third-party pure-Python module outside Python's Standard Library, at least until they've reached a wide measure of community acceptance.