Your workflow is unique 👨💻 - tell us how you use Dropbox here.
It would be extremely helpful to have the ability to download a PDF (or image, or other file types) with comments included. Alternatively, could there be a way save out just the comments as it's own ...
YES, this is essential! I work in publishing and authors like the comment feature, BUT you've made it into a task for us to TRACK the changes. We all need tracking for legal reasons and responsibility. It's NOT useful to download the comments IN the PDF (like PDF commenting) - but rather to be able to download either a text file OR a PDF (archival record) of the comment list is absolutely essential AND it's NOT hard to do. Why haven't you yet?