It would be nice if the mobile experience (or both) would use a simple javascript confirmation box when hitting "flag". Flagging seems like it should be an exceptional action and it simple to just hit "ok" as a confirmation step rather than trying to find what you accidentally flagged on the page to unflag.
We're probably going to extend 'flag' to give people a better way to report dupes, and that will require a confirmation, so yes. In the meantime, there's an unflag link, so misflags are undoable.