I believe that if you share a prototype and people leave comments online, and then you "share again" to update the screens in that prototype, the comments stay intact.
But if you update the prototype and share it to a new link (because you don't want to overwrite the old prototype, you want to keep it available for testing or maybe for historical reference), there will not be any comments since it's considered a new prototype.
My question is whether there is any way to transfer (or export or download) all the user comments from one prototype and then add them to the new prototype, since the comments may contain useful information for developers such as style formatting or rules for how to build certain interface pieces that pertain to all prototypes and it's tedious to have to copy and paste them from an old link to a new link?
I don't think this feature is available yet, and I couldn't find a feature request on the XD feature request page Adobe XD: Feature Requests: Hot (1048 ideas) – Adobe XD Feedback : Feature Requests & Bugs
If you don't find a similar request here either, I suggest creating your request. The team can prioritize the request based on the traction it gets.