dont recall ever submitting the same post more than once though.
If a report is submitted more than once, the first can be marked as good while the second may be marked as bad. I have mistakenly reported a post two times before but the moderator marked the second as bad.
Possibly the after the first post got handeled, the data of 2nd report had some interference with db (if the first one had already been resolved then 2nd served no purpose)
Do you see those 2 reports in your dashboard, along with marked status?