Hi,
I'd like to help you on this. I have a huge experience with .net development and have completed similar assignments here on freelancer.com as well, please feel free to check out my related projects.
Thanks to your concise requirements I believe it is fairly clear what you are after and I have a good overall understanding of the project.
I am considering saving the comment as metadata on the file (extended properties). Is this ok with you? Can we expect the application to have read-write permissions on all shares? If not, this would not work, so I'd need to store the comments locally (in an XML file).
My bid is for delivering this application within 2-3 days, tested on my end - making it available to you as soon as I'm ready and then be prepared to make any minor amendments that may be necessary following your testing/review; submitting complete sources (VS2013 solution, with application being developed using C#) that are sufficiently commented, in line with best design & coding principles.
Additionally I will be available going forward for any future improvements you may need.
Will supply skype contact details and ready to start upon awarded & escrow completed.
I look forward to working with you.
regards,
Janos