Would be better for the Reporters in a Spam thread to see if the post already is reported and that would also be against double reports and bad reports !
Is only a suggestion.
It would be better if a warning popped up rather than removing it completely but I do agree that something should be put in place. But I would think that if a post has more reports then it goes to the top of the queue so if someone has already reported it there is no need to worry about double or multiple reports. I understand from an individual viewpoint so that they don't report it twice to avoid their report accuracy going down or wasting their time.