If someone made a habbit of reporting the same posts over and over it'd be noticed and we'd know something was up.
I bet loads of people do it just to wind the moderators up
there was this one time where a guy spammed 500+ reports with multiple alt accounts. wasn't really a problem for me though, because I made a script in 90 seconds that marked them all as bad. :p
You really shouldn't even have to do that. If there are multiple reports on the same post, then once one is handled, SMF should make all of them as being handled....I don't see why you would take one action based on one report and then take another based on another (maybe it could display all of the comments for all reports for a post when you are handling a report on that post so a moderator can get "all" the information being reported regarding that post).
If SMF is not currently capable of doing this, then maybe this should be added to the requirements for features of the new forum