I would like to see not only the marks in the PDF export, but also the notes as annotations; visible also in other PDF viewers. The display with the annotations on the right side unfortunately does not cover this.
I would also like this to be the case. To do so, I think that MarginNote has a unique calling that it will have to split itself into two different applications. One application must be fully compliant with all other PDF editing tools but would likely provide no study tools. The other application will remain as it is, not be compliant with any other PDF editing tool, and have a robust set of “study tools”.