Add more options other than "Marked Fixed" in Collaborator. Marked Fixed can be confusing. Options: Mark Fixed Mark Closed Concur with Reject Concur Withdrawal
I have a feeling that the preferences for additional values could vary by customer, so if additional buttons / options are added, would be nice to make them optional. For code/document reviews I personally like the simplicity of the single "Mark Fixed" button, but renaming to "Mark Closed" could be a bit more universal; possibly could add a field indicating the reason for closing the defect, but this could be already done by adding a custom defect field.