Hi Fiverr,
I only wish to give some powers to sellers as well, Some buyers take advantage of giving a potential review if we do not fulfill their unwanted/not-mentioned requirements like extra revision, including source file etc. etc. they don't give feedback when the project is completed, they come after a few days with some more changes/revisions, if we deny they can give a negative review as they have power. we are very much dependent on the buyer's attitude. and feedback after cancellation is also in their favor. we mutually canceled the order because of some misunderstanding or mismatch in requirements but they can still give feedback(can't be positive I believe).
I hope you will consider it.
Thanks