I also came looking for a way to delete reports. My reason is that I installed an add-on called "Alter Ego" which is meant to show the Staff when someone is logging in with more than one account. (We don't allow it).
Problem is, Alter Ego created a report (because I checked the option) that ALL mods can see, even mods that are mods of a single forum. Reports are supposed to be viewable by Mods that moderate the specific forum(s) related to a post report. THis, however, is not a report related to a post, so apparently ALL mods could see it.
I meant for Super Mods and Admins to see this feature (and the reports), the general public is not meant to know it exists or if someone wants to hide their identity (not allowed at our forum) they will find ways to circumvent it. (yes... we've disabled it now from creating reports, but after several NON-SuperMods commented on the Alter Ego Reports that showed up, the Reports are still there visible to any Mod that Clicks Reports.)
If I cannot delete a Report, then it will be common knowledge we have this tool deployed.